I need to change my Apple ID because the email is no longer valid

See the instructions in Change your Apple ID - Apple Support

and be sure to note the following from that link:

Before you change your Apple ID

Sign out of all Apple services and devices

that use your Apple ID. If you want to use your iPhone, iPad, or iPod touch to change your Apple ID, stay signed in with your Apple ID on only that device.

if you are the original owner, take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store.

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or contact Apple ID Support. They will need to see the original purchase receipt/paperwork also.

Apple ID Support

Apple ID Support (2) 

Apple Support by e-mail or chat         Select your device, Battery, Power and Charging, then Power adapter not working to get a chat option. 

Apple Support using Twitter

Or fill out and submit this form.

If I no longer have the email addy, I cannot sign in to sign out of all services and devices. The ipad is locked with old email which is invalid now. expensive paper weight