....hook up the 9200 drive to the 9242...transfer the recordings to the external drive....put back the 9242 drive...transfer the recordings from the external drive to the 9242 drive.
Success!!! It works!!
I disconnected the SATA and power cables from the 9242 drive and connected them to the 9200 drive. No need to break the seal on the 9242 hard drive cage:
The 9242 booted up as normal without asking to format or the 311 error, BUT..... I could NOT see the recordings. Had an idea and cleared NVRAM and rebooted the receiver. BINGO!! Recordings from the 9200 drive are there and playback fine.
Note that clearing NVRAM will delete all your favourites, settings and timers. I would try it first without clearing NVRAM.