I know that most of the M4P files are DRM-ed and common converters are incapable of converting. But with a screen recorder, you can record all songs and save to MP3 format.
I use the Apple Music Converter for Mac, it helps me to get rid of the drm protection and convert Apple Music M4P to MP3 with ease. Thanks so much, my friends.
I use the Mac system, AppleMacSoft DRM Converter for Mac software is quite good, I suggest you use it.