Sorry, we are not familiar with the specific USB cords provided with the Iomega drives. Most external drives are just plug and play with the included USB cable. I believe that they provide an additional USB pigtail with mobile external drives in case the customer needs to use an additional source of external power.
I am surprised that there were no instructions included with the drive, either printed or on the software CD. Maybe check with Iomega customer support if no documentation was provided with the drive?