PA for converting M4A files into mp3 files in folders?

I just started with iTunes for podcasts and I discovered that most if not all files are in m4a. My little mp3 player doesn't do m4a files.

I have all my podcasts episodes split across 600 folders, randomly named so that I get a nice mix of podcasts.

I just discovered the m4a issue and don't want to manually drag and drop files into a program.

Is there a program that does it with the same functionality as a similar program such as Remove Empty Directories?

Where in the program, you specify that folder and it scans for all folders in that subfolder and deletes empty directories, but in this case, it scans for all m4a files and converts them to mp3 automatically?