Dell MD3200 add disk

Hi, 

our customer have  PowerVault MD3200 External SAS RAID 12 Bays Array with Dual Controllers (4 Ports per Controller). They have 4 x 3 TB disk in RAID-5 with Hot-Spare disk configuration. Now they buy new 4 x 6 TB disk and I install them in SAN. After installation I choose new disk Group, configure RAID-5 without Hot-Spare disk, start initialize and done. There was necessary to choose LUN (I don't know what is that and I choose 255). I read somewhere that it is necessary to change RAID Controller module same like previous RAID so I change and that, but still I can't see my new storage in Disk Management and I can't used. I attach and image with my Host Mappings. Please help me how to show my new storage and use it normal