Im getting a 3080 i have a seasonic focus 850w psu and i have a 1080ti with with a pci-e using connector 6 and 8 pin off one conncetor and i cant seem to find another pci-e cable in my cable bag so i was wondering if that will be sufficient for a 3080 dont i just plug both 8 pins off one connector into the new 12 pin adapter and plug it in on founders edition?
i saw some aib cards have 3 pci-e connectors and since i dont have another pcie cable could i use a pci-e cable from a seasonic focus 650w power supply and mix it with the 850w one? would it work and be safe? same psu just different watttages.

thanks in advance