I think I am stupid, it is not working for me, please see attached how I have done it with two different setups
In your photos, you create object powerup0 & powerubnumber that means that you'll create objects like powerup00, powerup01, powerup02, ...., and that's not what you want, you want only powerup & powerupnumber so it'll be powerup0, powerup1, powerup2, ... the only thing is that the initial value of powerupnumber should be 0. Then, you have to set it's value to (powerupnumber+1)%(how many animations do you have), so in your pictures should be 3.
If you still have any problems, post your .capx please
L. Edit: Only the setup where you have 3 different animations is good. The other one where you have 3 different frames isn't going to work.