Thank you, den.thed for useful guide and Jeff Donald for corroboration. In your first reply, den.thed, you recommended an adaptor to go from Thunderbolt 3 to Thunderbolt 2 as a first step. However, from the 'System Report' below I assume that my Thunderbolt ports are Thunderbolt 2:
Thunderbolt Bus:
Vendor Name: Apple Inc.
Device Name: iMac
UID: 0x0001000D1824A000
Route String: 0
Firmware Version: 23.10
Domain UUID: 07D399EB-CC56-8C56-AED9-65FB909A744C
Port:
Status: No device connected
Link Status: 0x101
Speed: Up to 10 Gb/s x2
Receptacle: 1
Link Controller Firmware Version: 0.12.3
Port:
Status: No device connected
Link Status: 0x101
Speed: Up to 10 Gb/s x2
Receptacle: 2
Link Controller Firmware Version: 0.12.3
So do you agree that I DON'T need the 3 to 2 adapter but can go straight to Thunderbolt 2 to FireWire 800 and then to Firewire 400? I should have mentioned that the scanner is Nikon Super Coolscan 8000ED.
My first time using this discussion group, so I'm grateful for your help.