Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Good day STEFANIE
From your description, I see you are trying to make your iPad appear under your Microsoft account devices list.
Please note that iOS may not work the same way as Windows PCs or Surface devices, as they are Microsoft-supported hardware for service/warranty management. The Microsoft's article Manage devices used with your Microsoft account currently says macOS and mobile devices cannot be added/registered there, so an iPad may not show in the Devices list even if Microsoft 365 works on it.
Therefore, if your concern is only that the iPad is not showing in the device list, that may be expected behavior.
Hope this could clarify things. Feel free to post back if you need further support!
Best regards.