Sorry, I don't think there are any adapters that will inter-convert a SATA port and a Firewire 800 port. They are just too different. It make much more sense to have a PCIe card with a Firewire 800 controller on it to create a real port.
Alternatively, look at your external drive unit. Does it have ANY other connection port on it besides Firewire 800? Maybe eSATA or USB? I know, USB2 is SOOOO much slower that Firewire 800, but it does work. And if it happens to have USB3, that's a fast communications link. Then see if your computer has a matching port to work with.
MAYBE. The info is limited and unclear to me. But it appears to connect your choice of eSATA, USB2 or Firewire 800 to a SATA port. It needs a power supply from a common Molex 8981 4-pin connector. What I cannot grasp is whether one of those connections is to a mobo port on the host computer to provide your choice of connections to a peripheral device (hard drive), or the other way around - choose one type of mobo port to connect a SATA HDD to. And I can't figure out where and how it is mounted. I found one accessory seller's site for a related CalOptic product that indicates it allows you to use a SATA port in the host to connect an external HDD unit via USB2, Firewire (400 or 800) or eSATA, so that is the type of connection you seek.
Whether it works or not is unknown. I could not find any reviews or comments.