Answer :
There is no 'cylinder below'. But I think you've told us enough about it
so that we can answer your question.
The volume of a cylinder that's standing up is
V = (pi) x (radius)² x (altitude) .
Fill in the numbers we know: 252 m³ = (pi) x (6 m)² x (altitude)
Divide each side by (pi x 36 m²) : (252 m³) / (pi x 36 m²) = altitude
7 / pi m = altitude
2.228 m = altitude (rounded)