Is it the one where you have to rescue the Dead-6, including Hotwire, Gunner and such? The really big level that takes place in a village and you meet up with local resistance fighters along the way?

To find the people there, simply follow your objective compass (the thing on the upper-right hand corner of your screen). It'll lead you to the various people.

Sometimes you may have to backtrack a little, and if so, the in-game EVA map (push "M") will help you find your way around.

Does any of that help?