10,000 square metres equals 1 hectare. Cubic metres would define a 3 dimensional object which a hectare does not describe.
there is one cubic meter that fits exactly in another cubic meter
You can't convert that - those are quite different things.
This is not really a valid conversion because cubic meters is a measure of volume while meters is a measure of length or distance.
This cannot be done. A cubic meter is a volume and a square meter is an area.
1200