Never mind that the phrase "В здании три входа" seems very Russian, the English translation does work naturally in some circumstances.
E.g. If I'm standing outside a large department store wondering why my friends haven't met me outside by the door to the store cafe where I'm standing, I might ask, "How many entrances are there to the cafe?" and the reply might well be, "There are three entrances in the building."
I'm sure it's very difficult, if not impossible, to construct practice phrases that work in Russian, British English, American English, Australian English, etc!
I agree. In my opinion, it partly seems to depend on the context and location of the speaker. If I am inside a building, I could easily say "there are three entrances in this building". While when outside a building it would probably be "to this building" or into.
I was wondering if this could also be translated as "the building has three entrances". I still don't 100% understand the concept of в has "in" versus the possessive quality.