how do I get 8 mm film transferred into imovie

Ok, there are 2 ways to transfer.

First, a Digital 8 Camcorder, simple, u pop in ur old tapes, then via firewire you can transfer them into iMovie.

Second, a device that takes A/V input and has firewire outputs to go to iMovie, I forget the name of the device but this is a possible solution.

Other then that, you cannot simply hook up that camera to the iMac.

Borrow someones DV camcorder...

Most recent DV camcorders have AV > DV converters which allow you to put the camera into "tape" mode plug the analog camera with the Mini-Jack you described into it and then with a Firewire cable, connect the DV camera to your computer. It will pass thru the signal, converting it to DV for iMovie.

There are stand-alone AV to DV converters, but if this is a one-time deal, see if someone has a camcorder that you can borrow or rent. If you're considering buying a camcorder just make sure it has the converter and firewire (IEEE 1394) in/out, most so. If this is a regular occurrence consider something like a Canopus device. http://www.firewire-1394.com/canopus-advc55.htm