In the board game risk transformers, when we exchange 3 robots for a vehicle, where do the 3 robots go?

in the game, Risk Transformers, it is said in the manual that we can exchange 3 robots for a vehicle AT ANY TIME. So, We take the vehicle from the scrapheap, remove the three robots from a zone, and put the vehicle in theyre place, right? The question is, where do the three robots go after that? In the Scrapheap? In the Operational Robots pile? or is there some new pile we make?In the board game risk transformers, when we exchange 3 robots for a vehicle, where do the 3 robots go?I don't know the transformers version. but in regular risk you put the 3 "Bots" into the pile where you draw the "Vehicle" since in reality they are exactly the same just a vehicle takes less space.