It's useful to know how to work out the volume of various common 3D shapes. Here are the main ones:

Note that it's normally not required for you to learn these formulae "off by heart" as they are usually provided on the examination "formulae sheet" (obtain an example of one of these to check). However, you will need to be familiar with the formulae, and you'll need to practice algebraically rearranging the formulae as this is a common way examiners will try to test you on two different aspects of the syllabus at the same time (i.e. shape and algebra).