Millimetres are used to measure length.
Area is measured in units squared.
Cubic metres and litres are not related.
There are 100 centimetres in 1 metre.
There are 100 metres in 1 kilometre.
There are 1000 millilitres in 1 litre.
Millimetres, centimetres and metres are all related.
Volume can only be measured in cubic metres.