What should I do if I find a sum of money exceeding 400 US dollars in a desolate, uninhabited, unvisited area, and it is land owned by my father?

If money is found on owned land, the default is that it belongs to the landowner if he claims it. Otherwise, it is considered a lost item (Luqata), because a lost item is that which is found in an unowned place. However, there might be evidence indicating that the money does not belong to the landowner, in which case it is treated as a lost item.