В случае если найдут запрещённое вложение, его изымут.

В случае если means if / in the event that.

It is basically a more formal, official-sounding version of если. You often see it in regulations, warnings, instructions, legal texts, and bureaucratic language.

• Если найдут... = If they find...
• В случае если найдут... = In the event that they find...

So the sentence sounds a bit more formal than everyday speech.

This is a very common Russian pattern: 3rd person plural with no stated subject.

It does not necessarily mean a specific they. It often means:

• someone will find
• people will find
• inspectors/staff will find
• if it is found

So найдут literally looks like they will find, but in English we often translate this more naturally as a passive:

• If they find a prohibited item...
• If a prohibited item is found...

Russian often uses this structure where English would prefer the passive.

Because Russian and English behave differently here.

In Russian, when the condition refers to the future, it is normal to use the future tense after если:

• Если найдут, изымут.
• literally: If they will find, they will seize
• natural English: If they find, they will seize

So this is completely normal Russian. English usually uses the present tense in the if-clause, but Russian uses the future.

Найдут is the 3rd person plural future form of найти (to find).

Breakdown:

• найти = perfective infinitive, to find
• найдут = they will find

Because найти is perfective, it does not have a true present tense. Its “present-looking” forms actually refer to the future:

• я найду = I will find
• они найдут = they will find

Because the adjective and noun must agree.

• вложение is neuter singular
• so запрещённый changes to запрещённое to match it

So:

• запрещённое = neuter singular
• вложение = neuter singular

Together they mean prohibited attachment/enclosure/item depending on context.

Also, in this sentence вложение is the direct object of найдут, but since it is inanimate, its accusative form is the same as the nominative. That is why it looks unchanged.

Вложение literally means something inserted inside something else. Its exact English translation depends on context.

Possible meanings include:

• enclosure
• inserted item
• attachment (for example in email)
• contents inside a package/envelope

So the grammar is clear, but the most natural translation depends on the situation the sentence comes from.

Because его is the form needed for a direct object.

Here его refers back to вложение and means it in:

• его изымут = they will seize it

Compare:

• оно = it as a subject
• его = it as an object

So:

• Оно запрещено. = It is prohibited.
• Его изымут. = They will seize it.

Even though вложение is neuter, the object form is still его.

Изымут means they will seize / confiscate / remove.

It comes from the verb изъять, which is a fairly formal or official verb. You often see it in legal, administrative, customs, or security contexts.

• изъять = perfective, to seize/remove
• изымать = imperfective, to be seizing / to seize repeatedly

So:

• его изымут = it will be confiscated / they will seize it

This verb sounds more official than something like взять or убрать.

For the same reason as найдут: Russian is using an indefinite-personal construction.

• изымут literally = they will seize
• but the meaning is often more like it will be seized

The sentence does not care who exactly performs the action. It is understood that some authority, staff, or officials will do it.

So the structure is:

• if they find X, they will seize it
• natural English: if X is found, it will be seized

Because the sentence begins with a subordinate clause:

• В случае если найдут запрещённое вложение = subordinate clause
• его изымут = main clause

Russian separates these with a comma:

• В случае если найдут запрещённое вложение, его изымут.

This is standard punctuation.

It is natural Russian, but it sounds formal and official.

What makes it formal:

• в случае если instead of plain если
• изымут instead of a more everyday verb
• the overall impersonal, regulation-like wording

A more everyday version might be:

• Если найдут запрещённое вложение, его изымут.

That still sounds fairly official, but slightly less bureaucratic.

Russian certainly can use passives, but in sentences like this it often prefers the indefinite-personal active:

• найдут = they will find
• изымут = they will seize

English often prefers the passive:

• If a prohibited item is found, it will be confiscated.

Russian frequently avoids that kind of passive when a simple 3rd person plural verb can do the job. This is very common in notices, rules, and instructions.