Yes, there is a free version of known software that can help you tag MP3 files on Mac. The name of the software is Tagger and it can be found on the official website of the developer hosted at GitHUB. Access the page and download the application, then you should be able to edit the files you have on your Mac.
Software requires: OS X 10.8. Higher versions are mentioned to be compatible with, but the software should work.