camera help nikon d3000 lens?

I have a nikon D3000, my nephew likes gadgets and things like that, well I bet you can see where this is going, fortunately I got to him before the camera was disassembled but I have only recently discovered that he managed to take the back part of one of my lenses off, re - assembling the back part of this lens has become more than I am capable of doing I need some assistance from someone who knows what they are doing, what I have is pretty simple, it's just the rear lens and three screws that are about 1/4 inch in length (all the wires are still connected) found the three screw holes but with further inspection I discovered that just inserting the screws will not attach the back part to the camera lens I need help, please. I haven't really tried to connect it, I figured that I would get some info from someone who knows what they are doing before i make an attempt, I'm pretty good with gadgets and stuff I just don't want to mess this up.

There are three screw holes and three screws but it looks as if it may not be just that simple to re- assemble. Because of the nature of this problem i cannot take it to a professional, please help.