8x SP120 connector questions

Hello there I wanted to surprise my son with a new computer and I recently purchased a corsair 900D. I bought 4 Corsair sp120 fans to replace the 3 stock fans in the front and the 4th for the top. I thought the fans had a 3 pin connector and so I am not sure what type of splitter or fan controller I can purchase to connect the fans to the PSU or motherboard. Also the cables are rather short on the fans.



My computer building skills are limited so if anyone can help me I would be so thankful!