In/on 5th floor

1. Much respected Mr. Wong __ 5F is trying his wife's undergarment.

2.  I saw the known loving couple __ 10F is hitting each other.

3. I saw the usually tough & strong Peter __ 9F is crying.

Which preposition should I use to fill in the above blanks, in or on?　

Teo,
Can you explain this again, please, with more details?
The blanks are placed where prepositions are not used, so I feel the exercise is wrong, or incorrectly copied, or something. 
Besides, the sentences seem to have nothing to do with "in/on the fifth floor".  (It's "on the fifth floor", by the way.)
Jim

Okay, in the above paragraph the designations 10F, 9F, etc refer to room numbers not to the floor they are on.  So it is correct to say Mr. so and so in (room) 10F.

If the writer wants to refer to the floor, he should say Mr. Wong on the 5th floor as CJ mentions above.