This revision aid for L1/L2 (mainly L2) Pearson Edexcel Functional Skills maths gives a side-by-side comparison of perimeter, area and volume, the sort of units that would be involved with each and a worked Functional Skills example of each with a PAV mnemonic for remembering which is which. I have also looked through the last few years of Pearson Edexcel FS for the sorts of questions that require each one.
Note: All images from Pixabay, so do not need crediting.
FM Complex multi-step problem(s)
FM L2.3 Evaluate expressions and make substitutions in given formulae in words and symbols
FM L2.16 Calculate perimeters and areas of 2-D shapes including triangles and circles and composite shapes including non-rectangular shapes (formulae given except for triangles and circles)
FM L2.17 Use formulae to find volumes and surface areas of 3-D shapes including cylinders (formulae to be given for 3-D shapes other than cylinders)