Dear Lisa,
Good day!!
I understand your concern and to my knowledge, I would like to convey that the Forms or Quizzes created in the Microsoft Forms will not be deleted even the number of Forms or Quizzes reached the limit.
Since you have mentioned you have viewed all the tabs in the Microsoft Forms but not able to find the old forms, I would like to request you access My Forms tab and scroll down in the page to click on the Recycle bin to find whether you are able find the old forms.
If there is no success in finding the missing forms even in the Recycle bin of the Microsoft Forms, I would like to immediately recommend you to connect with the IT admin of your organization (How do I find my Microsoft 365 admin? - Microsoft Support) and request them to connect with the Microsoft Phone support team via creating a new service request from the Microsoft 365 admin center, where they can investigate from their end and try to restore the missing form in your account.
Reference: Get support - Microsoft 365 admin | Microsoft Learn
Note: We apologize for redirecting you to related development support team because the moderators in this community are limited with the resource for further investigation and to get a quick resolution to your problem, we requested it.
If you are using the Microsoft Personal account (****@outlook.com) where the old Forms are missing, please let us know where we will guide you with further steps.**
Appreciate your patience and understanding. Have a great day!!
Best Regards,
Sophia