Gravitational potential energy is given by the equation GPE = mgh
So if the masses are the same, and gravity will always be the same as long as we stay on earth, then the only thing that is changing here is the height. Since picture 3 is lower then 1 and 2 it has the least amount of GPE since its height is lower. Since picture 1 and 2 are at the same height they must have the same GPE as everything in the equation would be the same.
Hopefully this makes sense and helps!