You can't convert mp3 to wav in WMP. You will need other software to do that. To solve your problem surely all you need to do is to create an audio CD from the the mp3 files in question.

If you are searching for best WAV to MP3 converters for PC, read this article. We have covered select online audio converters and desktop clients.

Windows Media Audio, or WMA, files contain audio data that can be played back in Windows Media Player, the default music player in the Windows operating system, and various other audio software.