Ipod to usb adapter?

I recently bought and installed a new Pioneer stereo for my wife’s 2003 Honda Civic. The stereo was ipod ready, so I assumed there would be a usb port to which I would plug in the usb to ipod adapter cable. However, the stereo had a cable with the male end of the ipod cable to plug the ipod into. I was hoping to be able to also play music from a flash drive. Is there such thing as an adapter to go from the male end of an ipod cable to a usb port? Thanks.