Windows doesn’t display your PC’s serial number anywhere in its
interface, and neither do popular system information tools. But you can
often find a PC’s serial number with a simple command, a peek in your
BIOS, or on the hardware itself.

The windows command is wmic bios get serialnumber and you can easily run it from a command prompt as follow.

– Click on the windows icon, type “cmd” in the search text box and press enter.

The command prompt windows will open.
Type the command wmic bios get serialnumber, press enter and the bios serial number will be appeared on your screen