Kilometrajul apare în cartea de service.

Because Romanian usually puts the definite article at the end of the noun, not in front of it.

• kilometraj = mileage / odometer reading
• kilometrajul = the mileage

So -ul here is the masculine/neuter singular definite article. Kilometraj is a neuter noun, and in the singular its definite form is kilometrajul.

No. They are related, but not the same word.

• kilometri = kilometers
• kilometraj = mileage, the total distance shown on a vehicle’s odometer

So kilometrajul does not mean the kilometers in a literal plural sense. It means something more like the mileage or the odometer reading.

Apare is the 3rd person singular present tense of a apărea, which means to appear.

So:

• eu apar = I appear
• el/ea apare = he/she/it appears

Here the subject is kilometrajul, which is singular, so apare is the correct form.

Yes, but in this kind of sentence it often sounds more natural in English as is shown, is listed, or appears.

In Romanian, a apărea is often used for information that shows up in a document, record, website, or report. So the idea is that the mileage is present in that document.

Because cartea is definite: it means the service book, not just a service book.

• carte de service = a service book
• cartea de service = the service book

In this sentence, the speaker means a specific service book, usually the one belonging to that particular car.

After în, Romanian normally uses the accusative case, but for many nouns the accusative looks the same as the nominative.

So:

• cartea can be nominative
• cartea can also be accusative

That is why you do not see a special extra ending here. Romanian has cases, but the form does not always change.

Carte de service is a fixed expression in car-related Romanian. It means service book, maintenance record book, or service booklet.

The word service is a borrowing and is very common in Romanian, especially in car contexts. It refers to maintenance or repair servicing.

So cartea de service is the booklet or record where maintenance history is written down.

Because in Romanian, in expressions of the type noun + de + noun, the second noun is often left in its basic, indefinite form.

So:

• cartea de service = the service book
• not cartea de serviciul

This structure works a lot like English noun combinations or of phrases. The first noun is the main one, and the second noun explains what kind of book it is.

Yes. Romanian word order is fairly flexible.

The version you have:

Kilometrajul apare în cartea de service.

is neutral and natural.

But you could also say:

În cartea de service apare kilometrajul.

That version puts more emphasis on where the mileage appears. Both are grammatical, but the original sentence is the more straightforward one.

A rough pronunciation is:

kee-lo-me-TRAH-zhul ah-PAH-reh uhn KAR-tea deh SER-vees

A few helpful points:

• j in kilometrajul sounds like the s in measure
• apare has stress on pa
• service in Romanian is usually pronounced SER-vees
• în contains the Romanian î/â sound, which does not match English exactly; a rough uhn approximation is good enough for a beginner

So the whole sentence is approximately:

kee-lo-me-TRAH-zhul ah-PAH-reh uhn KAR-tea deh SER-vees