There are 10 Marauder Camp Quests in Days Gone needed for the Marauder Camp Hunter trophy
The first two are part of the storyline and the remaining eight, you need to do some specific encampment jobs.
#1 - Story Mission (Cascade Region): Drifters on the Mountain
#2 - Story Mission (Cascade Region): Smoke on the Mountain
#3 - Lost Lake Encampment Job 2/7: Drifters at Eden Hall
#4 - Cascade Encampment Job 5/6: Here’s a Little Chaos
#5 - Lost Lake Encampment Job 6/7: He’s Just a Kid
#6 - Belknap Encampment Job 7/8: Rippers, Rest in Hell
#7 - Crater Lake Encampment Job: Just Doing My Job
#8 - Crater Lake Encampment Job: A Bunch of Cavemen
#9 - Crater Lake Encampment Job: He’s Feeding the Freaks
#10 - Crater Lake Encampment Job: How Do I Get Them?
Credits of this guide goes to PowerPyx from YT