Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Using your account at https://account.microsoft.com/services , install Office on the new PC. For more on activation, see https://support.microsoft.com/en-us/windows/activation/activate-microsoft-perpetual-products-using-the-product-activation-portal . You may have to contact Microsoft support if the activation portal doesn't work for you (https://support.microsoft.com/contactus ).