Since you have lodged this on the Vegas Pro forum, I assume that you are asking about how to find your Vegas Pro serial number. If this is the case, go to My Account on MAGIX's webpage and then to My Products. You will find there all your registered MAGIX products along with their serial numbers.
If you are asking about about the Dell computer itself, you should go to Dell's webpage (www.dell.com I think) and look through their tech assistance pages and FAQs. The answer may even be your computer's user manual.
@kris-wilkerson The answer should be on your pc. My understanding is that your pc ID is automatically picked up on activation and the identity that appears is the "Device Name" under Device Specifications in Windows 10 Settings/System/About. Try using that.