Are you talking about the case fan needs a little 2 or 3 pin connector to work and your PSU doesn't have one? They sell little adapters for them to fit the large 4 pin hard drive plugs, or you can simply buy a new fan. They price for the adapter is usually the same as the whole fan. And the generic fans already work with the large 4 pin hard drive connectors.
But if you are trying to plug the power supply onto one of the fan connectors on the motherboard... that is not needed and would probably fry your board. Perhaps the old HP PSU had a wire going from that to the PSU or case fan. But your current PSU does not need that. It has a working internal fan.
In other words, from the PSU to your board should only have the large 20/24 pin connector and the 4 pin connector for the CPU. No other connections from PSU to board are needed. The rest of the PSU wiring will go to the hard drives and other peripherals.
the connector im talking about is a 4 pin, on the hp website they call it the "Motherboard Fan power". it is slightly to the right of the actual fan on the motherboard. while i was writing this i was playing with a 8 pin psu connector, and realized it could split apart into two 4 pins, that fit whatever the unused connector on the mobo is. Awesome. i think this solves my problem, thank you very much.
That 4 pin connector is the CPU voltage connector. Has nothing to do with fans. The power supply will only connect to the board with 2 connectors. A large one with 24 or 20 pins, then a small one that is 4 pins, and sometimes 8. That is the connector that split into 2 4 pin connectors. Fans may connect to the board, but the PSU will only connect in those 2 places.