Miscellaneous topics that do not fit into specific categories.
When you first activated Microsoft 365 (Office) that licence should have become associated to your Microsoft Account as a digital licence online and it is from there that you can download and install Office without the need for a product key:
https://account.microsoft.com/services/
Please Note, if your version of Office is a standalone version like Office 2019, 2021 or 2024, not a subscription to Microsoft 365, then older versions of Office like 2019 will not work on a new MacOS device, you need to have Office 2021 or 2024 or a subscription to Microsoft 365.