In older devices nonvol is in region 41, in newer it's in region 154. If one is populated the other is empty anyway. I think your Drive 61 has MTP setting so will write to 2/: for the microSD, 1/: being the path to the internal RWFS. Dumping both regions will get the backup one way or another:
Spoiler:
rrgn,41,2:/41.bin
rrgn,154,2/:154.bin
reboot