Hi Tin Man. I'm Greg, a Volunteer Moderator and 10 years Windows MVP here to help you.
If you bought Windows 10 retail licenses from Microsoft they were most likely Digital Licenses and not Product Keys. But if there were keys then they'd be in the Order History in your online MS Account here:
https://support.microsoft.com/en-us/help/402731...
Windows 10 uses mostly Digital Licenses so that if you need to move a retail License it can be done fairly easily via the Activation Troubleshooter which is explained here:
https://support.microsoft.com/en-us/help/20530/...
If that method doesn't work by signing into the same MS account on the new hardware and running the Activation Troubleshooter to see if it finds the license and offers to move it, then you can contact Microsoft Support at https://support.microsoft.com/help/4051701/glob... or at https://support.microsoft.com/contactus choose Get Help, then Contact Us toward the bottom, then answer Yes you can Sign In, then Select Product: Windows, then tell the Issue, it should offer Messaging and/or a Call Back on week days.
As long as you have the Order History information or Product Key then they will always honor moving the key to new hardware on a retail license.
I hope this helps. Feel free to ask any questions. Based on the results you post back I may have other suggestions if necessary.
______________________________________________
Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.