activation lock came on to iPad and we can't remember the password. i tried on your support site but it does not recognise the very old email

If your device is Activation Locked, this help page will provide most of the information that you’ll need:

https://support.apple.com/en-us/HT201365

If you have forgotten your AppleID or associated password, these can be recovered here:

https://iforgot.apple.com

To recover your credentials, you’ll need access to one of the following:

• Your primary email address mailbox that corresponds with your AppleID
• Any of the secondary/recovery email addresses that should be configured for your AppleID account
• Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID

Unless you AppleID account has not been fully/correctly configured, or has been seriously neglected, recovery of the AppleID and password should not be difficult.

More information about recovery of your AppleID:

https://support.apple.com/en-us/HT201354

More information about recovery of your AppleID password:

https://support.apple.com/en-us/HT201487

When you recover access to your credentials, you would be well advised to log-in to your AppleID account from a web browser - and verify/update any email addresses and trusted telephone numbers:

https://appleid.apple.com

If the iPad is activation locked, the only way to get it released is to sign into the original Apple ID that it is attached to and have it removed. If you cannot get into the old Apple ID, then I’m afraid that is nothing you will be able to do to get past this. You can try to get in touch with Apple to get the account fixed so you can log into it, but that is going to take getting in touch with Apple and seeing what they can do for you.