Scratch

Ok so i'm doing an exam for computing in which i have to make a game called botmod, the objective of the game is the move your robot around and collect all the passengers on the map and return them to base without running out of power units.You start with 150 power units and each move costs a power units, the cost of power units per move is determined by the your traction and the terrain you are on on the map.What i need help with is programming the mods for the bot, the parts which impact the amount of power units used each turn. There are tracks, wheels and skis,i just need help with choosing your mods at the start menu and them then being applied to the bot in-game.Like for an example, i have a menu at the start of the game labelled ''Mods'' once this is clicked you will be presented with 3 buttons, Skis, tracks and wheels how do i make it so when i click on one of those it will apply it to the bot and have an impact on the amount of power units used per turn. Any tips and or tricks will be appreciated, thanks in advance