Hello
Yes, you can use your Windows 10 Pro key to upgrade your Windows 11 preview version to the Pro version. Here are the steps you can follow:
Disconnect the internet connection of your PC.
Press Windows key + I, then go to System > Activation.
In the right pane click the “Change” beside the Change product key option, then use the generic key VK7JG-NPHTM-C97JM-9MPGT-3V66T to upgrade to Windows 11 Pro.
Once you upgraded to Windows 11 Pro, connect your internet to the PC then use your valid Windows 10 Pro product key to activate the system.