This question is incorrect.The correct question is here
You have purchased a new 24-pin power supply to replace one that failed. However, the motherboard only has a 20-pin connector. What should you do?
Answer:
To solve this problem you should plug the 24-pin power supply into the motherboard, as your mother board has 20 pin you leave pins 11, 12, 23, and 24 on the motherboard unconnected.
I have attached a picture from which you can see that there are pins for same working
