Here are the filled-in blanks with the correct prepositions:

1. I last saw him **in** last March.
2. Section 5 is **on** the first floor of the Prep School.
3. You mustn't smoke **on** a bus.
4. Ahmet's grandmother died **in** 1990 **at** the age of 81.
5. Were there many people **at** the concert?
6. He speaks quite good French. He studied **in** Paris for a year.