You can install Windows 10 using the Media Creation Tool and skip the key entry. It will function with minor restrictions, such as a permanent watermark and disabled personalization settings.
If you need a new license, you can obtain one from several sources: download windows 10 key
Use this command for a similar result: (Get-WmiObject -query 'select * from SoftwareLicensingService').OA3xOriginalProductKey . You can install Windows 10 using the Media
If you have already purchased a license, the 25-character product key is usually delivered digitally based on how you acquired the software: download windows 10 key
Sites like Amazon or Best Buy typically provide the key in a "Digital Locker" on their website or via a receipt email.