I recently purchased a new Mac mini and it does not have a FireWire or Thunderbolt port. You will also have the same problem if you have purchased a very recent model MacBook Pro or iMac. The problem is I have quite a nice 3CCD Panasonic video camera that has a FireWire port on it. I need a Firewire to USB-C adapter but Apple don’t make one. They are changing ports faster than they can make new adapters.
Thankfully, as I found out today, you can plug your FireWire cable into a ‘FireWire to thunderbolt’ adapter and then you can plug this adapter into a ‘Thunderbolt to USB- C’ adapter. IT looks a mess but it works.
It may not be pretty, but the signal gets through. My computer was able to control the video camera and the video was able to import into QuickTime.