Firewire 400 to USB C
For anyone struggling with old external Firewire only hard drives to MAC USB-C. Don't waste your money on transfer cables. Just buy an old USB external drive case (I found one for $10 at a local used computer shop) and move your hard drive from the firewire case to a USB case. It's really easy.
Most hard drives will use ATA plugs - one for the power and one ATA data ribbon cable. So just unscrew the drive from the case frame and it will pop right out. If you want to cover the odds of the other style of connectors, they are called SATA plugs.
Now I just have to deal with a pile of useless firewire drives and cases.