I don't believe the optical drive power cable is proprietary however the motherboard in your computer has an 8 pin power plug instead of a 24 pin. You would need the following adapter to plug into your motherboard.

https://www.amazon.com/gp/product/B01A210HKO/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Delta Huntkey 850 can go as low as $40, if buying used bothers u then buy two of them, this is your easiest option

Only those two power supplies can be used with original case cables --> if u buy a different brand then only use the cables that come in its box (PSU cables don't interchange between brands)(and sometimes not even between models within the same brand)

ODD cable adapter for aftermarket type like EVGA G3 850, is a micro-SATA / slimline sata, try eBay Amazon google > example or Dell 1YMGT or slimline etc

Aftermarket types can get cramped, original 850's eziest due to custom-fit cables

_______________________

'motherboard in computer has 8p power plug instead of 24p'

What are you talking about, of course it has a 24pin

NO NEED FOR 24-TO-8P ADAPTER MENTIONED BY OTHER MEMBER

THANK YOU SO MUCH! Excellent advice that I will follow.