I’m looking for some pictures and serpentine belt?

Those belts don't fall off normally. I would look at all of the items it touches as well as the tensioner to determine if there is a problem before putting the belt on. The image is the routing of both belts on that engine. If you only have on belt it's possible the other one failed and that caused the one that was left over to come off. I generally recommend to replace both belts at the same time, plush check the other components.