Connect your aircraft to the ground station computer using a micro USB cable
Launch the Mission Planner Program
Open the Mission Planner’s Flight Data screen
Select the “DataFlash Logs” tab on the
Click the “Download DataFlash Log Via Mavlink” button
Then, select the log you want to download. This will save that log to your MissionPlanner/logs directory, in a folder named after the vehicle type, such as QUADCOPTER.