Resetting Graid to factory specs to start over

I started to back up on my New Graid 12 TB drive but had in wrong format. I want duplicate files on each drive. Not sure how to cleanse so I can reformat. I erased but still cannot get to reformat. Can someone tell me how to do this please. I had started to back up and realized I was in Raid O and wanted to be in Raid 1 to get duplicate back up. If anyone can help with this I would appreciate it since my Mac memory is nearly full.