Flight management reset

hi ı use pixhawk 2.4.8 and want to reset it . ı think to press flight management reset button but ı am not sure about that because ı have never seen any people who did that before . if ı want to reset it what should ı do ? wil ı have to upload something in it ? do you have an idea about that ?

ı tired to upgrade firmware on qground but ı couldnt upgrade ardupilot ı could upgrade just px4 and ı tried to do it again on mission planer but this time ı coulndt do bout of them