Length is normally measured in metres, written m.
We can have larger or smaller units of length by inserting a prefix before the unit letter: e.g. kilometres (km), centimetre (cm), etc.
Area is measured in square units, such as m², cm² etc.
Volume is measured in cubic units, such as m³, cm³ etc.
The litre is a useful unit for measuring volumes of liquids.
There are 1,000 L in 1 m³.