Hold up. You absolutely do not need any adapters. Your psu came with plenty of modular cables for that. And they are
not interchangeable. It does not matter the pin count on the psu side. That connector is just a connector, it could have 4,5,6, or 10 pins, wouldn't make a difference.
On the back (depending on version of that psu) is 5x straight 5pin connections, and either 3x or 6x 6pin cube connections. The 5pin straights are for periphials such as Sata or hdd or floppy or molex. The other cube 6pins are for pcie. Those psus can come with 6x 6+2pin pcie. One side has just a 6pin and plugs into the psu. The other side has a little 2pin dongle attached to a 6pin pcie. You physically connect the dongle to the pcie and get an 8pin pcie.
Don't try plugging in seperately. You have to join them together (they are keyed) before plugging into the gpu.
Ignore the fact the psu is Semi-Modular. For all intents and purposes, when you plug a cable into the psu, it's exactly no different than any of the wires that are in that giant bundle. The only benefit of Semi-Modular is that if you don't need a cable, you don't have to add it. So there's no big bundle of un-used wires hanging out making a mess in the bottom of your case. So the actual connection pin count can be ignored, it's just a plug. The other end, that goes to the gpu is the only thing that matters, if you needed a 6pin and 8pin, you'd simply plug in 2x pcie cables to the psu and both the other ends to the gpu, leaving one dongle hanging loose.
@tennis2 . Seriously? A 75w 6pin to 150w 8pin single adapter? Are you trying to burn something up?