iMovie doesn't recognize my Sony camcorder-help please

[bladerunner6]

My father in law has some equipment he wants to sell and he asked me to make a movie of it and burn it to DVD.

We did the shooting, but I can't find my cable for my Sony MiniDV camcorder DCR-TRV18, so I went to the local computer store that sells cables cheap and bought a cable from them.

Unfortunately, I could not get it to be recognized on my iMac, my MIL's Mini or the MacBook Pro in the computer store. The store even let me try a second cable and that didn't work.

The guy at the computer store said he thought I needed a specific cable from Sony and I don't agree with that.

The question is this: do I need a specific cable from Sony, a software patch for iMovie, or is my camera busted. Also if the FIrewire port on the camera is not working, can I use the USB port to copy the files to the HD and then import those into iMovie?

Thanks in advance.

Mike