Trouble with WD easystore
How do I get my new 1T WD easystore to reformat to run on my older Mac Pro. I've used all the tricks I can find on Disk Utility. I can't even erase this drive because:
"Unmounting disk; couldn't unmount disk; Operation failed."
All I really want is to transfer files from my old Mac Pro to my brand new iMac Pro
Help!
Mac Pro, OS X 10.11