batch convert audio files in vlc
I haven't tried VLC for batch conversion, or CLI alternatives, but searching on Google returns Mediahuman on first place. It's a free app and it can work with .wma.

I haven't used it -install with care, watch for uninvited crapware.

I've used fre:ac with great success for batch processing. It's open source and free. 


  It currently works with MP3, MP4/M4A, WMA, Small Vorbis iconVorbis,
  Small FLAC iconFLAC, AAC, WAV and Bonk formats.