Let's get something very clear, DO NOT use ANY power supply cables that did not either come WITH the power supply you are using OR another unit from the same series, from the same manufacturer, that you can 100% verify has the same pinout.
If you do, you will likely be replacing either the power supply, the motherboard OR the graphics card, and potentially, all of them or even other things. Don't do it.
If you don't have the correct 6+2 pin PCI/PEG cable, then you either buy a set of cables that are specifically intended for use with your unit or you buy another power supply. Or you have yours sent to you. You don't use a 4+4, because that is for the EPS CPU 12v and is entirely different. Again, you will let out magic smoke if you try that. Don't do it.
Those are pretty much your options.
Given the age of that power supply, and I'd say it's about ten years old, at least, based on when I know that unit was being manufactured, it's probably a VERY TERRIBLE IDEA to use it with anything you value anyhow. That was about a five to seven year unit to begin with, based on quality and what I know regarding how most very good units were built back then compared to now, and if it were MY hardware, there is no way in hell I'd use that old MK III with a fairly new RTX 2080 Super that likely cost anywhere from 600 to 800 bucks. No way.
Below you will find MY standard list of recommended power supplies and beyond that this thread is intended as a landing place for questions or discussions regarding specific units, platforms or related PSU tech, all of which are all welcome to be discussed here. If it's related to power supplies...
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