You can still upgrade to Windows 10

If you are still running Windows 7 or 8/8.1 you can still upgrade to Windows 10 for free.

Go to this Microsoft page https://www.microsoft.com/en-gb/software-download/windows10 and download and install the Media Creation Tool. Run the tool from within your existing Win 7/8/8.1 environment and follow the instructions to do an upgrade in-situ. (Alternatively use the tool to create installation media on a USB stick and install by booting from it.) Once the Windows 10 upgrade/installation is complete it should show as activated in the system info.