Each Mission has its specific win conditions. Tap on the button on the top of the screen while on a Mission and the Mission conditions will appear.
When all conditions have been met, the exit area will highlight so you can leave the area behind. Of course, this still means all your team members need to make it out alive.
When all conditions have been met, the exit area will highlight so you can leave the area behind. Of course, this still means all your team members need to make it out alive.