Since retail copies of Office 2021 require a Microsoft account for setup, your license is almost certainly recorded in the cloud. This is the easiest and most reliable way to reinstall your software without needing the physical key. Microsoft Learn How to Find your Windows and Microsoft Office License Keys
A critical point of confusion is the difference between the product key and the installed license key. When you activate Office 2021, your computer does not store the original product key you typed in. Instead, it stores only the of the activated license key. The full key is hashed and verified against Microsoft's activation servers. ms office key finder 2021
You can use a built-in command to retrieve a partial product key. Since retail copies of Office 2021 require a