What filesystem do you want to format it to?
Welcome to LQ
And what partitions are you looking to format on the drive? Or if it's "all of em" then post up what you get when you type:
/sbin/fdisk -l
And tell us which drive you want to format.
The short:
mkfs -t FILESYSTEM /dev/hdxx
Where FILESYSTEM is the filesystem you want, and /dev/hdxx is the partition(s) you want to format.
Cool