Mac: how do I select external drive 1 to be recovered to external drive 2 ?

[perpendicular]

Hello,

it is already a big problem following these instructions http://www.cgsecurity.org/wiki/PhotoRec_Step_By_Step But I will try and I hope I don't destroy anything. I am not used to command line and feel like doing something with bandaged eyes.

I have 3 disks:
a) is where my OS is on
b) is a drive that had been formatted and I want to get the files back (external drive enclosure)
c) is another external drive, 3TB with 2TB free space. Here I want to write the recovered files to.

How do I tell them to use the correct drive and not delete a and c?

[cgrenier]

Usually /dev/disk0 is the main disk, /dev/disk1 the second disk and /dev/disk2 the last one.
The disk capacity may help you to know which is which.
To select the destination under Mac OS X, you have to select the mount point, usually under /Volumes.