@ the op - I'm not bashing you or what you have, I'm just being brutally honest with you.
That doesn't make it a good idea. Those motherboards are meant to serve their OEM purpose and maybe some minor upgrades. The fact that this MB doesn't even use a 24pin indicates the "quality".
I went that route of upgrading a pre built and it ends up being more expensive and a bigger headache than it's worth. Fortunately mine despite being an average consumer PC had a proper MB with minimal proprietary crap.
I looked at his/her MB in the prebuild and it's so bottom of the barrel, I think a Wish.com MB would be better. I don't even think whatever CPU that's in there is getting full power and if it somehow is, it will bottlebeck a 6600.
But I'm not judging, like I said, OP can do what they want but getting into adapter Territory should be last resort, not to make a standard part compatible.
This MB is bad even by OEM standards. Look how far the 6+4 EPS (CPU) connectors are apart from each other. There is also an MMF and SFF variant that are equally sketch.