The entire point of enums is to make your code more readable and maintainable. You should use them anytime you need to represent an enumerated set of elements.
However, in this case, final/constant is more appropriate since you are representing a value (number of boxes, and number of pixels) not an enumerated set. If, say, you wanted to store types of boxes (metal box, cardboard box, ect) then you would use enums.