Hello,
I am trying to backup a 3790
model id 3xxxxxxxxx
006-D0397-00
FW5.10

Am I correct that I need to get the boot from a 5.10 gcd?
Should I use
rrgn,41,1:/41.bin
reboot

Or the rrgn,154,2:/154.bin ?
I've removed your device's Unit ID number from above to prevent any potential misuse of it.