Transferring film from an old JVC mini cam model GR-DV900AA to a MacBook Air 2020 via Firewire cable

The cable you show is not a FireWire cable. It looks like USB at the big end but can't be sure what the small end is , maybe mini USB???

Have a look at this link which shows the 3 cables that you need, yes 3 cables in all I'm afraid.

https://discussions.apple.com/thread/251304950

The first cable shown in the link is a FireWire cable. The small end plugs into your camcorder in the position shown in this pic'

The other 2 cables mentioned are adapters that enable the FireWire cable to be connected to your Mac.

You will need the 2 adapters as you have USBc ( Thunderbolt 3 ) ports on your Mac.

Be aware that importing Mini DV tape into iMovie is becoming more difficult with recent OSs. Some have success , some do not. The reasons for this are not clear. It may also depend on the make of DV camcorder being used.

Before investing about $£€ 80 on the adapters do you have access( friend , relative) to an old Mac that may be more successful in importing Mini DV tape?

Any chance of a picture or a link to where you bought this cable so that we can see what you are using?

Any information you can send would be good.

A picture showing both ends of the cable?

Not sure what you mean by "into the external port device that plugs into the Mac."

Apart from the FireWire Cable can you tell us what other cables / adapters you are using to connect Mac to camcorder?

You cannot connect a FireWire cable directly to your new MacBook Air.