storey - floor
You refer to the different levels in a building as its storeys or floors. If you are saying how many levels a building has, you usually use storeys.
They live in a house with four storeys.
The school is a single-storey building.
‘Storey’ is spelled story in American English. The plural of story is stories.
The hospital is a six-story building.
The hotel towers are each 30 stories high.
If you are talking about a particular level in a building, you usually use floor, not ‘storey’. Don't say that something is on a particular ‘storey’. You say that it is on a particular floor.
My office is on the second floor.
She rents a ground floor apartment.