The question mark is telling you the system can’t locate the OS files as it still is looking for the original drive (not yours) to boot from.
To over come that you need to use the startup key ***Option (⌥)*** to gain access to the startup manager. Then once running open up your preferences and set it permanently to your drive using the Start up drive setting.
Reference [https://support.apple.com/en-us/102603|Mac startup key combinations]