That mesh does not by default have any internal faces, so if you haven’t done anything to it there shouldn’t be any.
It’s very hard to give advice in the absence of any information about the thing we’re advising on. We don’t know what your mesh actually looks like, we don’t know what your material setup is, your environment/background, your lighting, nothing. It’s best to provide that information, either by supplying screenshots of all those things or more simply by posting your .blend file.