Hi kcab,
Well I know my DS7 has no clue what the conversions actually mean. If you asked him what is a pint and what would you use it for he would not be able to answer. So I suppose when to use what measurement and why? I know that is broad.

I don't know where to start. Should I just start with say length until he really gets it and then move on to say weight?

I dk why the schools he is in is skipping this topic.