@mikeghc here is the manual for it. yamaha_p-120_s.pdf. with that you can disassemble your Keyboard. The connector in question is JK101 and the Yamaha part number for that is V8149800
You can try and source the connector either from a broken board (it appears that most Yamaha Keyboards use the same connector) or you can measure the physical attributes and see if you can find a match at either mouser.com or digikey.com as well as any other place. Your keyboard is definitely repairable Let us know what you find.