forced to learn how upgrade

Feb 2, 2018
Gigabyte GA-Z68X-UD3H-B3
Intel Core I7 3.49 GHZ
Nvidia GeoForce GT 430
Mac Pro
Hello all,
I would like to upgrade my MacPro 3.1 Snow Leopard hackintosh to a Mountain Lion hackintosh.

My main confusion is this: Im new to all (any) type of upgrades. I have never built a hackintosh but i have one built from a old friend and now i don't know what to do.

I've seen a few guides on directly upgrading a hackintosh from SL to ML but I'm confused if I should just do a fresh install of ML, or upgrade from el capitan to mountain lion. My ultimate goal is to get it updated to high sierra.

I've wanted to do this for a few months now but i don't know where to start, i followed many tutorials but ended up in dead ins i also read the beginner forum but it confuses me even more.

If anybody can shove me into the right direction i will be forever grateful, and i hope to build my skills building and setting up computers and software like you guys.

Here are my specs: (hopefully this is the right, i opened up my computer and got names and searched on google).
3.49 GHZ Intel Core I7
2x XFX 6870 GPU (I know that Xfire isn't supported on Mac, but is this card technically unsupported still?)
Dual Bios Gigabyte
16gb nvidida sli, hyper x,
dual Pci express 3.0 (motherboard)

Thanks everyone!!!