Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
If the product is associated with a Microsoft account, you should be able to reinstall from the account at https://account.microsoft.com/services.
Note that if you purchased the product through your employer, as part of what used to be called HUP (Home Use Program), look at the Order History page at https://www.microsoft.com/en-us/workplace-discount-program/order-history.