Then, you need a firewire to Thunderbolt adapter. Apple sells this cable. Then you need a thunderbolt 2 to thunderbolt 3 adapter, which works for any computer with USB-C input. Resources ...

Years later, Apple would enable a FireWire Target Disk mode that allowed ... Ultimately, it brought similar functionality to USB-C and Thunderbolt (with the latter requiring a reboot on Macs ...