Assuming that the warehouse is a cuboid with flat walls and that the storage shelves also need to be heated, then:
3 ft = 1 yd
volume = 200 ft × 400 ft × 20 ft
= (200 ÷ 3) yd × (400 ÷ 3) yd × (20 ÷ 3) yd
= 1600000/27 cu yd
= 59,259 7/27 cu yd
≈ 59,259 cu yards
(at that size, the fraction is immaterial; it is also reasonable to round to the nearest 10 cu yd to give approx 59,260 cu yd.)
It is best to have the measurement of cubic feet of space of the area to be heated. This is the length of the space times the width of the space times the height. It takes far more to heat a 10 x 12 bedroom with 8 foot ceilings than it does to heat a warehouse that is 250 feet square with 16 foot ceilings, so be accurate with the measurements. You will also want to inform the rental business of the type of space: residential, commercial, a pole barn, temporary construction trailer, etc.
960 cubic feet
There is no conversion between cubic measures and square measures.
You don't. Metre measures length, cubic metre measures volume.
Cubic meters measure volume.
None. Feet are linear measures while cubic yards are measures of volume.
Cubic feet measures volume and inches measures length, there is no conversion between them.
Cubic miles measures volume. Square miles measures area. Therefore, you can not compare the two.
Weight measures the pull of gravity on the mass of body and cubic foot measures volume. You cannot convert the weight of anything to cubic feet.
Gallons, litres (liters), and lots of cubic measures - like cubic cm, cubic m, cubic miles, ...
cubic measures such as cubic feet, cubic meters
Both cubic meters and liters are measures of volume.