Hello T Mack and welcome!
Just out of curiosity, is there a specific reason why you want/need to convert mp3s to wav?
If you look around on versiontracker.com or google, you can find a lot of converters, but most of the ones that look reliable are shareware (not free) and the free ones look sketchy. But you can convert mp3 to wav in iTunes, which you should have on your Mac already. If your mp3s are already in iTunes, simply open iTunes, go into iTunes Preferences, click on the advanced tab, select the import tab and change the Import Using box to WAV. Click OK. Now just select the song or groups of songs (by clicking on one song then hold the SHIFT key then click on the last song you want converted), right click or hold down the Control key and click and select Convert Selection to WAV. Then it will take your mp3s and make them WAVs. FYI, you will still have your original mp3s in your iTunes library in addition to the WAV files.
I hope this helps you out. Let us know if you need further help
Cheerio
Searay