Thunderbold 1 or Firewire 800 to SATA III dock or enclosure...

I have a 15" MacBook Pro late 2011 (model A1286?). It is hobbled with USB-2 ports. It as a Thunderbold port (Thuderbolt 1?) and a Firewire 800 port.

I'm trying to find way to attach an external 4T to 6T hard drive. All of my searches end in a USB-3.x (type-c) or Thunderbold 3 (type-c) connections. I've tried to find a male Thunderbolt 1 to female Thunderbolt 3 adapter hoping for backwards compatibility but have found nothing. My understanding is Thunderbolt 1 to USB-3 is not possible due to hardware limitations.

There must be used Thunderbolt 1 or Firewire 800 docks or HD enclosures for sale somewhere but eBay, Amazon, etc. searches offer nothing.

I'm hoping someone here knows where I might buy a Thunderbolt 1 or Firewire 800 Dock or Enclosure that accepts 3.5" SATA III HD(s) and 2.5" SSD(s) with capacities of 4T to 6T.

Thank for any help you can provide!

Dave