Hello to all!
Having the need which the OP had, I happened to visit this thread and found out that most of the above suggestions were not working for me. I then was able to successfully have an .wma file converted to mp3 format by using Emicsoft M2TS Converter for Mac.
Under Profile select 'GENERAL AUDIO' and select MP3-MPEG Layer-3; then add your file. Click on the settings and select the sample rate, audio bitrate etc. as per your need. Next, when you click the button 'save as...' you enter the name of your song and click the button: youget your profile as User Defined and find the saved file name too. Click ok. Next browse the destination to which you want the file to be saved. Next click upon the START button and in a jiffy you are free to enjoy your mp3 version of your favorite song!
PS. the trial version of this Converter can convert files of 5 minutes or under. Above that duration, you need to buy this Converter.
Hope this will help all of you who have been looking to find a solution to this problem. It has worked fine for me.
Regards and have a great day.
Dr. Somanna