-- 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.