If your computer came preloaded with Microsoft Windows, the software product key is usually on a multicolored, Microsoft-branded sticker on your PC case or the bottom of your laptop. However, Microsoft has been changing and improving the way it handles Windows licenses. Windows 10 introduced a "Digital Entitlement" element to Microsoft's license which links your Windows key to an ID generated based on your PC's hardware. But because your hardware can significantly change if you upgrade your hardware, this entitlement was expanded to become a "Digital License" when 2016's Anniversary Update (1607) arrived.

 Do I have a digital license?

 The Windows 10 Settings app has a page for displaying your activation information, including whether you have a digital license, though your key isn't shown here: Go to: Settings > Update & Security > Activation

If you have a digital license, you should see "Windows is activated with a digital license" or "Windows is activated with a digital license linked to your Microsoft account."

Here is how to retrieve your product key. 

Please download the link below. Open the .zip file and double click on the Application called ProduKey. This will generate you extract your key in the next window that opens.