Reformating a 3 GB USB drive into just one partition
I once tried to plug a 3TB hard drive into my 2008 iMac to discover it wouldn't recognize anything over 2TB. So, I upgraded to 10.8.5. But evidently, when I originally tried to format the drive, I accidentally created 2 partitions. When I plug the device in, I now have "2 hard drives" - one 2.2 TB and one about 800 GB. I want to reformat these "two" drives into one usable 3TB drive.
Any suggestions?
iMac (24-inch Mid 2007), OS X Mountain Lion (10.8.3)