No way of knowing, to many variables.
216,000 ml
1 litre = 1000 millilitres so 216 L = 216 000 ml.
5.4L
1 liter = 1000 cubic cm 216 cubic cm = 216/1000 liter = 0.216 liter
216L = 7.63 ft³
No. Liters measure volume and horsepower measures work.
6 HP
6.38 L 1 liter = 33.814 oz 1 oz = 0.02 L
6 HP
Horsepower is not measured in litres. Litres is a measure of engine displacement, not power. Power is roughly proportional to displacement, but also varies with many other factors.
There isn't a direct correspondence between horsepower and displacement. It'll depend on the fuel type, thermal efficiency of the engine, programming (in electronically controlled engines), and other factors.
There are infinitely many possible answers. Two of the simplest answers are 216 + 0 = 216 and 216*1 = 216.