1. "look like a men" is not correct because 'men' is plural - it can't be mixed with the indefinite 'a'. You can however say something like "They look like men".
2. "look a man" is not correct either. You can however say "She looks a man" to mean 'she looks like a man' or you can also say "Look, a man!" which I know is probably not what you wanted to say, but it's in the same vein. Note the comma.
3. "look as a men" is also incorrect. You can however say something like "They look as men do".
I hope this helps you.