I don't know what sizes to use or even how to do it.
It is the bottom one.
I am no professional but from my take it looks like a 10", 8" and 6" which have been carved to that shape. Fondant has been applied to each tier, then fondant strips cut and applied for the stripped look.
I am sure the more experienced members on this board will jump in and help you out with the finer points. Good luck, very cute cake!
Nicole got it right
i second (or is it foutrth that??lol) but i would like to add that they look like they are either double barrel tiers or very high baked tiers of like 6" high