you have a computer? do a search for 'audio file converter'. I've used this ("Convert Audio Files To/From All Audio Formats with Switch" https://www.nch.com.au/switch/index.html) before. or, nero do software that is easy to use too.
I meant to add - because WMA, and mp3 are compressed file formats, the playback quality is not as good as uncompressed formats, such as flac, and aicc. flac is cd-like quality, but there are also websites that offer higher resolutions too. the downside to hi-res is that android auto won't play anything higher quality than flac.
WMA is a Microsoft audio codec, whereas the others are what are referred to as 'open source'. my understanding is that, because it is a Microsoft product, it was only really designed to play on equipment such as a Windows pc. perhaps the reason for your issues stems from the fact that Windows and Android are rival operating systems?