Yes, those are the exact words. I'm assuming it has something to do with the partition function, derivating it with respect to V, or N, or whatever, to obtain E, p, etc is probably the way to go. Then from that going to either the molecular weight ("to confirm that it is OK to treat it clasically").
Yeah I know the interactions are never really zero but some assumptions can be made to make life a bit easier for us, non-interacting molecules (or atoms, because it's monoatomic) would be one of them.
I'm guessing that by confirming the molecular weight (as only M, T and p are given in the question) one shows that it can be treated clasically, but if one gets a different weight then you've shown that "it cannot be treated clasically".