Generally, newer versions of Office do not have keys to find back. When using it for the first time, we need to bind Microsoft account to the Office license. Later, we can log in to the "My Account" page with this Microsoft account to check the Office products we own and download and install them.
Your Office was bought from Microsoft Hub which may be different with above, I want to help you, but the forum has limited resources to find back your key.
Here are 2 links I find that you may have a look and follow the guidance according to your situation.
Install or reinstall Office or Microsoft 365 through Microsoft Workplace Discount Program
Get help installing Office through Microsoft Workplace Discount Program
Hope the information could be helpful.
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