* Litres (L) measure volume. They tell us how much space something takes up.

* Cubic litres (L³) also measure volume. They are a unit of volume, just like litres.

You wouldn't say "how many litres in one cubic metre?" because both are units of volume. It's the same with litres and cubic litres.

So, there's 1 litre in 1 cubic litre. They're essentially the same thing.