"Where is the ninetieth floor?"
Translation:Hol van a kilencvenedik emelet?
Köszönöm! I knew I had probably forgotten some detail or another. This language is hurting my brain, hanem szeretem ;-)
If you have a question word in your sentence, you want to put that in the focus. That is what you want to have answered. The focus point is right before the verb in the sentence, so hol van has to stay together like that. You may also say "A kilencvenedik emelet hol van?"
Emelet ~ storey, floor (of a building)
Szint ~ level
I assume the original sentence is talking about buildings, so emelet seems more appropriate.