Doing some more order of magnitude approximations, in order to scale this black hole down so it were the size of our observable universe, define "the diameter of the universe in millimeters" (approx 10^30) as mmU. There are mmU * mmU * mmU * 0.5 mmU universes in the diameter of this black hole. For each millimeter in this scaled-down black hole, there are mmU groups of mmU universes, with another half layer of nesting, but then you can divide that by 1000. To fit the number of universes in the whole volume in a line end to end, repeat this process again, except without the extra half layer and division by 1000.
*Giving us a black hole with a radius large enough to fit about 112 googol observable universes stacked end-to-end in a line.
~Triple the number of zeros for the number of universes to fit in its 3D volume. 112 x (4/3) x pi followed by 336 zeroes, more or less.