Why doesn't iMovie 10 recognize my MiniDV Camcorder?

I have some old footage I need to transfer to one of my Mac Pro's, footage is from a Panasonic GS -12 mini DV camera. I have a mini dv to firework cable hooked into one of my OLD Mac Pros which have firewire ports.

When I open IMovie 9 it sees my camera but I get a communication error message. So I Did an iMovie update to 10 and now it does NOT see my camera. That Mac Pro is running 10.3.6 so I just need a firewire to thunderbolt cable and a thunderbolt 2 to 3 (USBc ) to do all this on my Mac Pro 2019 but do not want to waste the money on cables if my New mac pro will not see the camera. Any help here??

[Re-Titled by Moderator]