Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Try to work out the missing characters in the product key on your product key card.
If that is not possible the first option is to contact the retailer you purchased the Office licence/subscription from to ask them for a replacement.
If that is not possible, try contacting Microsoft support directly, provide them with proof of purchase and the other details on the card, they may or may not be able to provide you with the associated product key, try using this method to contact their support.
Go to this link: https://support.microsoft.com/contactus
Select Microsoft 365
Click 'Get Home Support'.
In the box provided, type billing.
Press Enter, then on the next page, scroll down and click 'Sign in to Contact Support'.
Navigate to Microsoft 365 and Office - Manage my Subscription.
Select the 'Chat with support agent in web browser' option