Cannot access older firewire drives on new imac

Hi

I am very frustrated - I have three G drives Firewire 400/800 models and when I connect them to my newer Imac, they are not showing up anywhere. Not in disk utility or in the About this mac window. I connected them using a Firewire 800 to Thunderbolt 2 adaptor from Apple as suggested by tech support, to no avail. Have reinstalled G Drive firmware, restarted several times. and tried each drive individually. They do not mount.

Any advice on this? Seem like it is a systematic problem since NONE of them show up.

help!!?? thanks

Try with USB, FW is an interface that has stopped getting support from Apple and you will likely have issues with the interface.