Assuming you're on PC: In the file folder containing the old version of the game, go to the "game" folder and locate the "saves" folder. Then, go to the "game" folder of your NEW downloaded version (which shouldn't have a saves folder inside) and create a new folder, naming it "saves" exactly the same as the other one. When that's done, just copy/paste the entire contents of the old saves folder into the new one and you should be set.
Assuming you're not on PC: I got nothing.