"I do not know their names."
Translation:Neznám jejich jména.
Yes, Portuguese has conhecer and saber. Conhecer is to know (a person), saber is to know (knowledge). Am I correct in assuming that nevím is for "I don't know the price of that article" and neznám is for "I don't know Pete" and also "I don't know his name" (a name being treated as something personal and not as a piece of knowledge)?
I was about to ask what other language you might know. Easier to explain via those than English. Znat is a knowledge you got without learning typically. Know a person, know a place. Vedet is a knowledge you achieved by study or by learning about some fact (even if from a gossip). You 'vedet' what is 2+2, where something is (including my keys), know who Shakespeare was, unlike 'znat' the neighbour that lives next door.