Pivot the mag. catch, and you will be able to indentify the pin which passes through it. Its right above the catch. The plunger which engages the mag. is held in place by the catch itself. Putting in an extended catch? Look at the new part, see where the pivot hole is, hold it against the trigger housing in the correct place, and you'll find the pin. It shouldn't take a lot of force to tap out the pin.
