No problem,
Good news, one of those will work no matter what model of GTX 950 you are hoping to use.
The side with the solid 8-connector will plug directly into the PSU (either of the red slots on the left will work), and the other side into the GTX 950. I'd personally recommend using the 6+2 cable on the left, and if your GTX 950 model only needs a 6-pin the extra 2 can hang off the side. Doing it that way will enable you to upgrade the GPU to a new model that requires 8 pins in the future without having to fiddle with your cables again. Using a 6+2 cable on a 6-pin GPU is quite common, and will in no-way hurt the card as the connections are designed to handle both 6 or 8 pins on the line.