In reality there are three 'worlds', but two of them are invisible to normal perception and direct measurement and belong to what science calls 'dark matter' and 'dark energy'. That's where all the various hells and heavens are, but you need the right instrument to see it, ie the purified concentration of the fourth jhana.
Three at less, because we dont know what is hidden. And it's just our Univers, i think, and Theory of Cords and Lindte Theory tel us that there is infinity of Univers, with different laws ets. Stephen Hawkongs speaks about 10 with 100000 zeros at less.
So if we take some tree leafs and compare with all leafs in the frest, it will be very optimistic.