Thank you Pekka!! I hadn't thought about trying to work on them in Windows, so I used Parallels and Windows 7, I was able to delete the partitions and shut it down. I put the drives into the RAID Box and connected it to my iMac and was able to use the Disk Utility to format the disk and set up RAID! That's the first time I've used Parallels since I set up this iMac!
The problem I had was with the My Cloud Box, for some reason it stopped connecting to the internet and I wasn't able to access the drives. I even went to WD's website support and they told me I would not be able to use the drives anymore. The drives don't have any bad sectors and shows the full 4 TB available.
Very happy now! Thank you for all your help!