How do I install a power supply on an OptiPlex 755 mini tower?

Hello, I bought a new Dell power supply a few weeks ago after I got the blinking amber light of doom   I had managed to replace the power supply a few years ago, however in my haste to remove the old supply I forgot to take pictures of where all the cables go and now I am completely lost. I have tried plugging it up but I keep getting a message of "drive one not found Serial ATA and SATA1.  It's got a lot of cords that I don't remember on the old power supply labeled from P1 through P9. If anyone could give me a simple explanation of how to plug these cords up I would really appreciate it because I don't want to have to buy a new computer. Thank you very much