Mission Planner - Getting position info - 3dr telemetry

Hi everyone, my first topic

When I using mission planner on ground, I can observe my position. But because my research requires some testing and position records, therefore I want to write on txt file. I can’t find the which part of mission planner radio code ( https://github.com/ArduPilot/MissionPlanner/tree/master/SikRadio ) or master.

Can you give any advice, i am too new for mission planner