Windows 10: Buying new computer. Can I find my current serial number and use it?

Hello, Is there a way to see what serial key my computer uses, and find out if it can be used on my new computer? I have three computers. Two running Windows 10 Pro, the third Windows 10 Home. I know at least one was upgraded from a Windows 7. One I know is a retail and the third I really can't remember if it is OEM, retail, upgraded or what... For some reason I only have one serial written down, but I am sure I have reinstalled windows 10 several times on all three computers. I would like to deactivate windows on one of the three computers and transfer it to the new one, but how can I be sure it is possible? Thank you

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Why some BIOS have and some didn't have serial no?

Hi!
Does somebody know why some BIOS have a serial number and why other dont have?

On some system if I run the powershell command
Code:

I get a serial number than on other I don't get a serial number or I get "System Serial Number" written.

Why is this?
How can I know before I buy a pc does it support serial number in BIOS or not?

The serial number is very important when we integrate the pc to Azure...

Thanks for any help and suggestion.

 

Computer Serial Number

HP needs the serial number to identify your computer (and determine whether it's still under warranty) but neither HP nor anyone else can access your computer just by knowing its serial number.

 

Serial number

The serial number should be on a sticker somewhere on the desktop.

You can also go into the BIOS to find the serial number.

This link has the info, it says laptop, but should be the same steps:

https://support.hp.com/us-en/document/c00034791