Поверх looks nice, literally "on top" or by the summit, peak, maybe верх.
In my native Ukrainian-speaking family we would use "Чи це восьма підлога?"
Literally: "Is this the eighth floor?"
"Поверх" is used to signify the "floor level" as in a department store,
or "story" as in the 'story (level of the floor) of an appartment building'.