Если я поеду в другой город, мне понадобится паспорт.

Если is the normal Russian word for if when introducing a condition:

• Если я поеду... = If I go / If I travel...

It is the standard choice for conditional sentences like this one. In everyday Russian, если is by far the most common way to say if.

Поеду is the 1st person singular future form of поехать.

• поехать = to set off, to go by transport, to travel somewhere
• я поеду = I will go / I will travel

This verb is perfective, so its future is expressed with a single word:

• я поеду
• ты поедешь
• он/она поедет

A native English speaker may wonder why this can translate as both if I go and if I will go. In English, after if, we normally say if I go, not if I will go. Russian still uses a future form here because the action is in the future.

Russian makes distinctions that English usually does not.

• идти = to go on foot, in one direction
• ехать = to go by transport, in one direction
• поехать = to set off / go by transport, perfective

So поеду suggests going somewhere by some means of transport, not on foot.

Also, поехать is perfective, which fits well in a sentence about a single completed trip or the act of setting off to another city.

If you said Если я еду в другой город..., that would usually sound more like If I am going / If I’m going (already arranged or in progress) rather than a simple future condition.

That is a very common question. Russian and English work differently here.

In Russian, after если, you can use a future form when the meaning is future:

• Если я поеду... = If I go... / If I end up going...

Russian does not avoid the future here the way English does. So although English says if I go, Russian naturally says если я поеду.

Because в with motion toward a destination usually takes the accusative case.

Here the idea is to another city, so:

• dictionary form: другой город
• after в with motion: в другой город

Both words change because другой is an adjective modifying город, and adjectives must match the noun in case, gender, and number.

So:

• город → город (accusative singular, same form as nominative because it is inanimate)
• другой → другой (masculine accusative singular, same form as nominative here)

Even though the forms happen to look the same here, the case is still accusative because of motion.

Russian often expresses need with the construction:

• кому? + понадобиться / быть нужным
• literally: to whom will it be needed

So:

• мне понадобится паспорт = I will need a passport

This is much more natural in Russian than translating English word-for-word.

The version with нуждаться в exists, but it usually means to be in need of and is less natural for ordinary everyday needs like documents or objects.

Compare:

• Мне нужен паспорт. = I need a passport.
• Мне понадобится паспорт. = I will need a passport.

The second one points to a future need.

Yes. Понадобится comes from the verb понадобиться, meaning to become necessary / to be needed.

Its form here is:

• понадобится = 3rd person singular future

Why 3rd person singular? Because grammatically the thing needed is the subject:

• паспорт понадобится = the passport will be needed

And мне shows the person who needs it:

• мне понадобится паспорт = I will need a passport

It is related in meaning to:

• надо = it is necessary
• нужен = needed / necessary
• понадобиться = to be needed, especially in the future or at a particular moment

Because Russian uses the dative case for the person who experiences the need in this structure.

• я = I (nominative)
• мне = to me / for me (dative)

So:

• Мне понадобится паспорт
  literally: To me, a passport will be needed

This dative construction is very common in Russian:

• Мне холодно. = I am cold.
• Мне нравится музыка. = I like music.
• Мне нужен паспорт. = I need a passport.

In this sentence, паспорт is the grammatical subject of понадобится, so it is in the nominative case:

• паспорт понадобится = a passport will be needed

That may feel strange to English speakers, because English would make I the subject: I will need a passport.

But in Russian, the structure is more like:

• To me, a passport will be needed

So:

• мне = dative
• паспорт = nominative subject

Yes. That is also correct and natural.

• Мне понадобится паспорт
• Мне нужен будет паспорт

Both can mean I will need a passport, but there is a slight stylistic difference:

• понадобится often sounds a bit more like will become necessary / will be needed
• нужен будет is also common and very straightforward

In many situations, they are interchangeable.

Yes, Russian word order is flexible.

The neutral order here is:

• Если я поеду в другой город, мне понадобится паспорт.

You could also hear:

• Мне понадобится паспорт, если я поеду в другой город.
• Если я поеду в другой город, паспорт мне понадобится.

These versions can shift emphasis slightly, but the basic meaning stays the same.

Russian word order is often used to manage focus and emphasis, not just grammar.

It can mean either, depending on context.

• другой город = another city / a different city

In this sentence, it most naturally means another city or some other city than the one I’m in now.

Russian другой covers both ideas that English often separates into another and different.

Yes. It is a normal future real condition:

• Если я поеду в другой город, мне понадобится паспорт.

It means the speaker sees this as a possible real situation in the future.

Structure:

• Если
  • future/perfective action
• result in the future

This is not a hypothetical contrary-to-fact sentence like English If I went..., I would need... In Russian, that type would normally use бы.

Here, the meaning is simply:

• If this happens, then that will be necessary.

Not in this sentence if you want to keep the meaning if.

Russian needs если to clearly mark the condition here:

• Если я поеду в другой город...

Without если, the sentence would not mean the same thing.

In some fixed expressions or conversational styles, Russian can imply a condition in other ways, but for a straightforward sentence like this, если should stay.

Yes, most likely. Поеду is perfective, so it usually suggests a single trip or a specific act of going.

If you wanted a more habitual or repeated idea, Russian would usually choose a different wording.

So this sentence sounds like:

• If I go / if I happen to travel to another city (on that occasion), I’ll need a passport.

That fits the perfective aspect well.