"What floor is it on?"
Translation:C'est à quel étage ?
There are a couple of mistakes in your sentence that make it ununderstandable. First étage is masculine, so it should be quel étage. Next, where is the subject of est? I would say that you wanted to use the expression est-ce que/qu' that we use in question. Then your sentence would be Quel étage est-ce qu'il y a ? = What floor is there? literally. It doesn't make a lot of sense.
What could have been is À quel étage est-ce ? or À quel étage est-ce que c'est/il est/elle est ?. Keep in mind that, unlike in English, you cannot end a question with a preposition in French. You have to put the preposition before the interrogative word.