Plug the USB Drive to PC , and check the disk:
fdisk –l

Assumtion : USB Disk at /dev/sdb

Unmount the USB
umount /dev/sdb*

 

Format the drive
mkfs.vfat /dev/sdb –I

DD the Image from ISO to USD Pendrive 
dd if=/home/hs.tan/source-cd.iso of=/dev/sdb

if : Input File ( ISO )
of : Output file (USB Drive)