Some cards with RAID can be set into a non-RAID mode, but that depends on the card. If that’s not an option and you’re using all hard drives on this card, you might be able to set each drive as it’s own array.
Can you see them in the Disk Management area? (Start/Settings/Control PanelAdministrative Tools/Computer Management)
If these are all hard drives, and new, you’ll need to format them and assign a drive letter before they will show up under My Computer. You can do that in the Disk Management section.