And a metre stick with millimetre or centimetre divisions works well for the different side lengths. Like a billion is a cube of length 1 metre, made of cubes

And a metre stick with millimetre or centimetre divisions works well for the different side lengths. Like a billion is a cube of length 1 metre, made of cubes 1mm wide. You can also roughly scale down by factors of 3 (square root of 10, roughly) by considering a 30cm ruler in place of the metre stick.