With plate tectonics, supercontinents split up into smaller continents, and then the smaller continents get mashed up together to form a new supercontinent. There used to be a single supercontinent Pangea, and before that there was Rodinia. How many times in the past have all the continents been smashed up together into a single supercontinent?
There's a fairly decent Wikipedia page about this: https://en.wikipedia.org/wiki/Supercontinent
In short, though, the question of "how many times has this happened?" is very difficult to answer because the further you go back in Earth's history, the less evidence is still left today from that time. Not everything can or will ever be reconstructed with certainty.