Any question answered...

^ i'm pretty sure the 'p' in m4p stands for protected.

This is probably why they aren't showing up in your music player. What phone do you have?

Galaxy note. I did try copying via usb, which kept asking me to convert them and then crashed.

m4p is m4a with copy protection - linked to your iTunes account in other words. Burn them to a CD in iTunes then rip them back onto your computer. If you use another program for the last stage you can keep them seperate so you don't end up with loads of duplicates.

I have 17,000 songs of which about 1,900 are protected. Not all purchased songs are m4p despite being bought from itunes. Dont have enough cds or time to burn and reinstall. Without going through every folder, I don't know what is protected.
I have a 1tb external harddrive. Is there any way to burn a virtual cd?