Ok, there seems to be some confusion here.
A premise is a step in an argument put forward toward establishing some conclusion.
A proposition is the meaning of a given sentence.
Since what you have given is a conditional sentence and not clearly an argument, I'd be inclined to say that what you have is a single proposition.
Now, depending on your view on propositions you might think that this conditional proposition has parts like the antecedent and the consequent. Likely these would also both be propositions.
So, to reflect your update, I'll update my answer. The argument that you give is, as you note, valid. It is an instance of modus tollens. The problem, however, is that it (plausibly) isn't a sound argument. The premise "If men evolved from apes then there wouldn't be any ape nowadays" seems very open to doubt. In fact, it seems to actually be false. Our best theory is that we evolved from apes. But there are, obviously, still apes.
I'm not sure what informal fallacy this argument contains, perhaps a hasty generalization or something? But the most damaging point is that I don't think the argument is sound since I think the conditional is false.