How to remotely sign out and reset previous devices

Hello there!

I just had a concern. I had a 15 pro max and iPad 10th generation earlier so I had my apple account connected with it. Now I have shifted to another device and gave that to parents. now they don't know how to sign out. I have all the credentials of the old devices. I just want to reset it from here as I live far from them. I want to reset the phones from my device giving all the login credentials so that my parents can sign in their own account.