We've already reached the limits of our universe to express these big number so we need to look beyond that. Enter the multiverse theory. The idea of having multiple possible universes gives us some more room to continue expanding the boundaries of big numbers.
According to the theories there might be up to an amount of possible universes in the multiverse expressed with a number that has so many zeroes that the number of telling the amount of them itself has ten million zeroes (10^10^10^7). So we could fill all the Plank volumes of all the universes in the multiverse to create yet another immerse number.
Adding zeroes can get us far, but we run out of universes at this point to just spell the number out (or the number of zeroes for that number if we want to take it a step further). We have actually already used the next step a bit while expressing the previous numbers: the exponent.
Exponential growth is, well, exponential. It gets big really fast, especially if we keep stacking them into so called power towers. For example 3^3 is 27, but 3^3^3 is already around 7 trillions. Adding one more and we are in the ballpark of googolplex and the 5th one leaves our multiverse-filled-with-zeroes number behind. And we can just keep going on adding more layers to that tower.
Using exponential operator we can reach again an entirely new order of magnitude. Where the commonly known math ends our journey to the truly big numbers is just about to start. But for that, we need to define some higher order math first.