How to format a USB flash drive?

go to super mode by typing "su" followed by super mode password

fdisk -l

that will show all the volume in your pc or you can also use the

df

to see the usb flash drive, suppose it may be /dev/sdb1

umount /dev/sdb1

that un mount the drive

mkfs.vfat /dev/sdb1

to format drive into fat32 format
EDIT
mkfs.vfat -n 'name_for_your_pendrive' -I /dev/sdb1
to add name for your pendrive