what should i do if i dont remember which apple id i am using on my restored ipad?

Your Apple ID

1. Forgot Apple ID

2. Forgot iCloud Password

3. Apple ID - Apple Support

4. Manage your Apple ID primary, rescue, alternate, and notification email addresses - Apple Support

Forgot Security Questions

1. If you forgot the answers to your Apple ID security questions - Apple Support

2. Apple ID- All about Apple ID security questions

3. Contact Apple for help with Apple ID account security - Apple Support

Another hint is when you attempt to activate the device, you will see the beginning letter of the email address, as well as the domain name for that email to help jog your memory about the Apple ID.