Look.

whom = которых (genitive)
of whom = из которых (genitive, I hope you remember the rule "if I see 'OF' it implies genitive"), like "one of whom" = "один из которых"
which = которые

activities of crediting institutions, of whom do not receive deposits (it sounds weird to me in English though, but I can be wrong, of course) = активы кредитных учреждений, из которых не принимают депозиты (if I've got it correctly, I'm not sure).

activities of crediting institutions, which do not receive deposits = активы кредитных учреждений, которые не принимают депозиты