bought new cpu. where do I find Microsoft product key?

Spence

body of what

TSTonyV

Hello @Spence! Welcome to the Community. 

Under your email I found a purchase for a new Dell laptop. Is that what you're referring to? If so, the product key would be digitally embedded in the BIOS on the motherboard, it won't be physically written anywhere on the unit. 

I'm guessing it may say something like your copy of Windows is not activated/not genuine? If so, make sure you're connected to the internet and make sure the date and time are set correctly. AFter that, click your Start Button, go to Settings then Update and Security. Once you're in Update and Security, click Activation over on the left, then click the Troubleshoot button. It should activate your copy of Windows. 

If you want to pull your product key because you want to write it down or something like that, you can follow this guide on looking up your Windows 10 License Key