Do you mind rephrasing that? Im kinda stipid lol.
The Wii U gamepad uses a
flexible printed circuit/flat flexible cable (FPC/FFC) to connect all the buttons to the gamepad's mainboard rather than using wires. The traces and contacts in flex circuits can be made of copper, silver, or a carbon material. Copper and silver traces can be scratched and soldered to directly, whereas carbon traces cannot be soldered to at all and require a connector. Since the gamepad uses carbon traces, you need what's called a
breakout board.
Breakout boards are a PCB that has a particular socket on one end, and a heap of through holes on the other end. Each through hole is connected to one pin of the socket, and are easy to solder to. Nicholas298 used them recently in his N64HHv2 project, circled in red.
Basically you get one with the right number of pins with the correct pitch (spacing between the pins in millimetres), socket the FPC into it, figure out the pinout for the FPC, and then you can solder wires to the through holes to connect the controls to your GC+ controller board.