Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Is Office 2019 added to your Microsoft account at https://account.microsoft.com/services ? In that case, use the account to install on your new computer.
For assistance with (re-)activation, see https://support.microsoft.com/en-us/windows/activation/activate-microsoft-perpetual-products-using-the-product-activation-portal .