access .m4p files

Did you previously ask Apple to deactivate the ID? If so, they say:

Can I reactivate my account?

Yes. If you request account deactivation, you'll receive a unique alphanumeric access code. When you're ready to reactivate your Apple ID, contact Apple Support, provide your access code and we’ll help you reactivate your account. If you lose this code, we won't be able to help reactivate your account. 

You will have to log into those accounts. Those are very old protected format files and will only play if authorized. Once you log into the accounts you can convert them to unprotected by taking out a subscription to Apple Music in one account and use Family Sharing.

Click on this link to read what to do "If you forgot your Apple ID" --> https://support.apple.com/HT201354

Click on this link to read what to do "If you forgot your Apple ID password" --> https://support.apple.com/HT201487

or go directly to this link --> http://iforgot.apple.com/

Also read about "What to do after [or before] you change your Apple ID email address or password" - https://support.apple.com/HT204071

If you still need help:

Contact Apple for help with Apple ID account security "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues."

https://support.apple.com/HT204169

I don't know if this iCloud terms statement extends to other aspects of having an Apple ID.

https://www.apple.com/legal/internet-services/icloud/en/terms.html

VII. B " In addition, Apple may terminate your Account upon 30 days’ prior notice via email to the address associated with your Account if (a) your Account has been inactive for one (1) year; or (b) there is a general discontinuance of the Service or any part thereof."