Older firewire cable on Mac 2019 adapter

Here is a link to the Apple USB-C to Thunderbolt Adapter you need to pair with the Thunderbolt to Firewire Adapter @Keith Barkley linked.

https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter

The adapter I linked paired with the adapter @Keith linked should work. I've used those exact adapters to access a Firewire drive and even accessed an older Mac that was in Target Disk Mode using the Firewire port. If it does not work, then you should contact the manufacturer of your device to see if they have any recommendations besides purchasing newer equipment.

https://www.apple.com/shop/product/MD464LL/A/apple-thunderbolt-to-firewire-adapter

However, you will also need a TB3 to TB1 adapter for it.