nimotu ga okuretara, tuisekibangou de sugu sirabemasu.

が marks 荷物 as the grammatical subject of 遅れたら.

So the first part is literally like:

• 荷物が遅れたら = if the package is delayed

Why not は?

• が is natural when you are pointing out what is delayed.
• は would sound more like setting up the package as the topic for contrast or discussion.

In many everyday sentences, either can be possible depending on nuance, but here が is very normal because the focus is on the event: the package being delayed.

All three can express something like if/when it is delayed, but they have different nuances.

• 遅れたら
  Very common and natural in conversation. It means if it gets delayed / when it gets delayed.
• 遅れれば
  Also means if it is delayed, but sounds a little more formal or conditional.
• 遅れると
  Often sounds more like a general consequence: when it gets delayed, then... It can feel less suitable when the speaker is talking about a specific action they will take in response.

In this sentence, 遅れたら sounds natural because it expresses:

• a condition
• followed by the speaker’s intended action

So it fits the pattern:

• If X happens, I’ll do Y.

This is a very common Japanese grammar point.

In the 〜たら conditional, you attach ら to the past/plain past form:

• 遅れる → 遅れた → 遅れたら

Even though it looks past in form, 〜たら does not necessarily mean past in meaning here. It simply creates the conditional if/when.

Examples:

• 雨が降ったら、行きません。
  If it rains, I won’t go.
• 着いたら、電話します。
  When I arrive, I’ll call.

So 遅れたら is just the normal grammar form for if the package is delayed.

Here, で means by using or with. It marks the means or tool used to do something.

So:

• 追跡番号で調べます = check using the tracking number

This is the same で used in sentences like:

• 箸で食べます。 = eat with chopsticks
• 日本語で話します。 = speak in Japanese
• スマホで調べます。 = look it up with a smartphone

So in this sentence, the tracking number is the tool/method used for checking.

調べます means to check, to look into, or to investigate.

In this context, it means something like:

• check the delivery status
• look up where the package is
• investigate the shipment using the tracking number

It is broader than just see or look. It has the nuance of actively checking information.

That is why 調べます fits well with 追跡番号.

すぐ is an adverb meaning immediately, right away, or soon. In Japanese, adverbs often come before the verb they modify.

So:

• すぐ調べます = check right away

This placement is very normal.

You can think of the sentence structure as:

• [if the package is delayed], [using the tracking number], [right away], [I check]

Japanese often places adverbs directly before the verb, though there can be some flexibility.

The subject of 調べます is omitted, which is extremely common in Japanese.

From context, we understand it as something like:

• I will check
• we will check

Why is it omitted? Because Japanese often leaves out subjects when they are obvious from context.

Also, 調べます is in the polite -ます form, which suggests the speaker is making a polite statement, often about their own action.

So even without 私が, the sentence naturally means that the speaker will do the checking.

It is a compound noun made from:

• 追跡 = tracking
• 番号 = number

Together:

• 追跡番号 = tracking number

Japanese often combines nouns this way. There is no need for の between them here.

So:

• 追跡の番号 would sound less natural in this context
• 追跡番号 is the standard expression

荷物 can mean several related things depending on context:

• package
• parcel
• luggage
• baggage
• load

In this sentence, because of 追跡番号, it clearly means a shipped package or parcel, not luggage you carry personally.

So context tells you which English word fits best.

It can sound like either, depending on context, but it most naturally suggests a policy, habit, or intended response:

• If a package is delayed, we check it right away using the tracking number.

Because there is no explicit time word like tomorrow or this package, it can sound like a general response pattern.

But in the right context, it could also refer to a specific situation:

• If the package is delayed, I’ll check it right away with the tracking number.

Japanese often leaves this kind of distinction to context.

The comma after 遅れたら helps show the pause between the condition and the main action:

• 荷物が遅れたら、追跡番号ですぐ調べます。

It makes the sentence easier to read, especially because 〜たら introduces the if/when clause.

However, in casual writing, Japanese punctuation can be somewhat flexible, so you may also see it written without the comma. The meaning does not change.

Yes. Normal Japanese writing usually does not use spaces between words.

The standard form would be:

• 荷物が遅れたら、追跡番号ですぐ調べます。

Spaces are often added only in learning materials to help beginners see the word boundaries.

So the spaced version is for study, not standard native formatting.