Save/load Adventure Game

So I am making a adventure game and I know how to logic edit and model and all that, but a mystery that I MUST solve is how to save and load a game in game. Meaning all the buildings that you bought and added into the scene will be saved in the position. I ran into some problems…

-The saver that I have will only save objects on the layer of because the other objects, that are added, are duplicates and carry the same name.

-I have seen a saver on YouTube by Totter333 that is remarkable and saves all objects added and in the screen. I dont know how this is done, but I think it has to do with adding a ID code to a object every time it is added, so each object has a different ID.