Importing Old miniDV Tapes Onto iMac Using iMovie

I have an old Sony DSR-20 professional DVCAM/MiniDV deck with low hours on it that I want to use to import content from tapes into my Late 2015 iMac that is running macOS v10.15 Catalina and iMovie v10.2.5.

The external drive that I plan on saving the media to will be connected via USB 3 or Thunderbolt 2. The deck, of course, will be connected via the four-pin "DV" jack on the back of the tape deck, which is a FireWire port, through a FW to Thunderbolt adapter and then a Thunderbolt cable into the Thunderbolt 2 port on my iMac.

The problem I have run into up until this point (previously on my MacBook Pro) was that the Import Capture appears to go smoothly until the end, then there is no prompt to save a file and no confirmation that it is successful.

When I check in the Finder at the designated destination that I had chosen in iMovie, no file has been created there.

WHAT STEP AM I MISSING? It seems like a waste of money to buy a dedicated importing program like LifeFlix DV Importer when I should be able to do this in iMovie. I have a feeling there is something simple that I am missing to save or create the file resulting from the import.

Thanks in advance for your advice !