Upgrading GPU in Precision 5810 (which cable do I need)

I have a Dell Precision 5810 that I use as my everything PC. It does 4K video rendering, photo workflows, general use, and some gaming. With Forza Horizon 6 coming out soon, there's a chance my GPU won't be enough for it, which is mainly why I'm here. Current specs wise, I have the Xeon E5-1660 V3 3GHz, 64GB ECC RAM, a mixture of M.2 and SSDs, Dell GTX 1070, and the 685W PSU. 

I am looking at upgrading the GTX 1070 to the RTX 3080 but I do know that will need more power. I'm looking at putting in the Dell 0V5K16 1300W PSU that I read will fit in the 5810 chassis. I mainly have a question about the cable though. Right now, the cable used to power the 1070 has an 8pin going into the Dell 0M6NP2 power distribution board, that splits off into an 8pin and a 6+2pin. The 8pin is what's feeding the 1070 while the 6+2pin is hanging in there. I do see that the 3080 needs 2x 8pin plugs, so my question is if my current cable will work, or if I need a cable which has 2x true 8pins, and not 8pin and 6+2pin like my current is now. 

Thanks for your help!