They do not use 3 8 pin connectors. they are using a single PCIe Gen 5 cable. Do not plug any PSU pins into the power connector unless you have a PCIe Gen 5 cable. (Which you don't) There are 2 versions of the RTX 4080 and each has it's own specific requirements. You don't need anything special since the adaptor is included in the box so you can connect them if you don't have a PSU that has a PCIe Gen 5 cable.   However, I would highly advise against purchasing an RTX 4080 for an R8 since it uses Intel 8000 CPU's, and they are way underpowered and cannot drive an RTX 4000 series card properly. All that will result in is the same frame rates as a 3080 card because of the CPU bottle neck.    
Greetings, I have Alienware Aurora R8 with 850 watt PSU. It has 2 pairs of 8-pin GPU connectors, 4 in total. Currently my GPU uses 2 8-pin connectors and I would like to upgrade to RTX 4080 blower (if available by any manufacturer). I reviewed specifications of RTX 4080 founder's editions and it uses 3 8-pin connectors. My question is, if I can use 3 of the 4 8-pin connectors because they bundled in pairs. Thank you.
Aurora R8, PSU GPU connectors