my old Apple ID was my work email which now no longer exists bc my old company deleted the email so i am not able to access it.
Correct, if you no longer work for that company, that company has already deleted your work email address. This is done as soon as you have left the company so that you can no longer log in. You no longer have any rights there.
An deleted email address, it is no longer valid, it simply no longer exists and it no longer works.
To understand about a deleted Apple ID, see the Apple articles below:
How to delete your Apple ID account -> How to delete your Apple ID account – Apple Support (UK)
-> Once your account has been deleted, Apple can't reopen or reactivate your account or restore your data.
Understand and control the personal information that you store with Apple
Understand and control the personal information that you store with Apple - Apple Support
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how to upload all of my old info/ iCloud backup (again i cannot just download the backup bc my former Apple ID no longer exists)
if you mean from your old company deleted work email, that is not possible.
