Which occupies mrs space, 3m cubed or 100ft cubed

The question is somewhat ambiguous.

-- It's hard to tell whether it's asking about  '3 cubic meters'
or  (3m)³ which is actually 27 cubic meters.

-- It's hard to tell whether it's asking about    '100 cubic feet'
or  (100 ft)³ which is actually 1 million cubic feet.

I'm going to make an assumption, and then proceed to
answer the question that I have invented.
I'm going to assume that the question is referring to
'three cubic meters'  and  'one hundred cubic feet' .

OK.  We'll obviously need to convert some units here.
I've decided to convert the meters into feet.

For 1 meter, I always use    3.28084 feet.

Then (1 meter)³ = 1 cubic meter = (3.28084 ft)³ = 35.31 cubic feet.

So 3 cubic meters = (3 x 35.31 cubic feet) =  105.9 cubic feet.

That's more volume than  100 cubic feet.