Old iPad transfer with email address no longer valid

Hi. Just switched to new iPad using transfer but it seems iPad was so old the apple account was tied to an email that no longer exists. On my work phone the Apple ID account is registered under my current work email. I tried to add the old one but it’s no longer valid so won’t let me. On the new iPad it defaults to asking me to sign in with the old invalid email address, I can’t seem to find a way to switch it to new one same as phone. As a result to access apple apos games etc I have to keep using old iPad. How can I get out of this vicious circle and avoid having to use two iPads for different purposes. Have searched self help links but it’s not immediately obvious to this amateur.Thanks in advance