How to make a GUI button "exchange" one item for another? [closed]

Okay so, I have a part in my game where when clicked on a gui pops up. I want the part to act as a "forge" or "furnace" in the game, where players can use it to "smelt" ores. Once the part is clicked, the gui that pops up has several buttons. Each button "smelts" a different ore (i.e. one button can "smelt" an iron ore into an iron bar and another button can "smelt" a steel ore into a steel bar). The thing is, I don't know how to make the button "smelt" only one ore at a time (oh and the iron ore is a tool). All i need is just one button, the rest I can "clone" and change the items. I will be very grateful, thanks!

P.S. By "smelt" I mean destroy the ore and add the bar into the player's backpack from the lighting.