As long as you are using the cables that came with the power supply they should be fine, you do not want to use a cable that came from a different power supply.
If your question is about the 8 pin or the 6+2 pin those will only fit in the proper connection unless you really force them. You can look at the plastic around the pins and you will see the difference.
Luckily the end that connects to the video cards and motherboards is all standardized so you can't mess it up. If you REALLY want to test stuff you can find the pin out diagrams that show what voltages each should have.