Broj za praćenje je u poruci.

Serbian often expresses this kind of idea with noun + za + verbal noun.

• broj = number
• za = for
• praćenje = tracking

So broj za praćenje literally means number for tracking, which is the normal Serbian way to say tracking number.

Praćenje is a noun meaning tracking or following.

It comes from the verb pratiti = to follow / to track.
Serbian very often turns verbs into nouns like this:

• pratiti = to track
• praćenje = tracking

So in this sentence, za praćenje means for tracking.

Serbian does not have articles like a or the.

So broj can mean:

• a number
• the number

Which one is intended depends on context. In this sentence, English would usually translate it as The tracking number is in the message, but Serbian simply says Broj za praćenje without an article.

Je means is, and it is a short clitic form of the verb biti = to be.

In Serbian, clitics usually appear in the second position of the sentence or clause. That is why je comes after the first unit:

• Broj za praćenje | je | u poruci

So even though English says The tracking number is in the message, Serbian naturally places je after the first phrase.

Because u meaning in takes the locative case when it shows location.

The basic form is:

• poruka = message

But after u for location, it becomes:

• u poruci = in the message

So:

• poruka = message
• u poruci = in the message

This is a normal case change in Serbian.

It is the locative singular of poruka.

Here is the pattern:

• nominative: poruka
• locative: poruci

Since the sentence is talking about where something is, Serbian uses the locative after u:

• u poruci = in the message

Yes. Since Serbian has no articles, u poruci can mean either:

• in the message
• in a message

Context tells you which one is meant. In many practical situations, especially customer-service or delivery contexts, it will usually be understood as in the message.

Yes. Serbian word order is more flexible than English word order.

This sentence could also appear as:

• U poruci je broj za praćenje.

That still means the same thing, but the emphasis changes slightly.
The original version:

• Broj za praćenje je u poruci.

puts the focus more naturally on the tracking number.
The version starting with U poruci puts more emphasis on where it is.

Yes, it is completely natural.

It sounds like something you might see in:

• a delivery notification
• customer support communication
• an email or SMS about a shipment

It is short, clear, and idiomatic Serbian.

A rough pronunciation is PRA-che-nye.

A few useful points:

• ć is a soft sound, somewhat like a very soft ch
• nj is pronounced like the ny in canyon
• stress in Serbian is not usually marked in normal writing, so learners often just imitate native pronunciation from audio

So praćenje sounds approximately like PRA-che-nye, though the exact ć sound is softer than English ch.

Yes, depending on context. Broj za praćenje is very common and clear, but you may also see related expressions such as:

• broj pošiljke = shipment number
• kod za praćenje = tracking code
• broj za praćenje pošiljke = tracking number for the shipment

Still, broj za praćenje is a very standard and natural choice.