Windows Command Prompt (cmd.exe) 1. Open CMD In Windows 8 and 10, press Windows logo key + X, then select Windows PowerShell, Windows PowerShell (Admin), or Command Prompt (Admin). Another way to find Command Prompt in Windows 10 is to search for and select Command Prompt. 2. Find the Serial Number. In the Command Window, as shown below, type or paste the following command: wmic bios get serialnumber The Printed Label Check for SN on the labels here.