No problem Flex, here's some more description:
The yellow powerup objects are just images that the player touches to trigger collection of an item from the array, so instead of "On collision between Player and PowerupObj" you can just trigger the event when a chest is opened/touched.
The global variable (In the project tab on the right) is how many different values there can be.
The first event under Start Of Layout just fills the array with "Powerup" and a number, eg: "Powerup1", "Powerup2", and so on.
You could just store a cash number in each of the slots instead, and then when the player reaches in to a chest it will return one of the cash values that was not already picked up before.