2017 iMac and External FW800 HDs

Hello folks.

I recently purchased a refurbished, 2017 iMac running Mojave. I'm upgrading from a 2010 MacBook Pro, which was running Yosemite.

The 9yo MacBook Pro's startup disc is dying. Fortunately, I backed up most of my files on redundant external HDs. But, on the newer iMac there are no FW800 ports. (I was aware of this at purchase time.)

But, the firewire HDs also have a USB port, so I connected one of these drives (with two more daisy-chained to it via their FW ports) to one of the iMac's USB-3 ports. I hope this is making sense so far.

There are no mounted drives, however, within Mojave. I only see the main startup disc.

Now, via firewire, I also have these daisy-chained FW800 drives connected to a machine running Windows 10. Because of Paragon's "HFS+ for Windows" program, I can mount these drives easily in Windows. So....

My question is, is there a way to access these drives via my Mac? Is there a hardware issue with the USB connections? Alternatively, can I access these drives via ethernet through my Win 10 machine?

Thanks much folks...

Keith