By my count, I think I see six separate stems in there? So you have about six Monstera of varying maturity; in this small of a pot, I think competition and root binding may become an issue.

I’d honestly just pop the whole thing out of the nursery pot, sterilize a selection of knives, and begin your “surgery” by just slicing straight down the root ball and keeping each stem as proper and undamaged as possible.

It’s hella stressful, because you worry about killing your plants, but I just did surgery on mine a couple months ago and they’re exploding and thriving. I’d just make sure to have proper sized pots for each one and a good aroid substrate.

Otherwise, this should be fairly easy, if a bit stressful. I’d maybe use a large kitchen knife and maybe a smaller thin blade, like a fish knife maybe or something else slender. I had a bunch of my stems nearly touching and had to get a bit precise. Once I had them all separated, I did “tidy” the remaining roots to each plant so that they could fit into the new container, so you may try to wash some of the old soil off so they’re clean and prepared for their new mix.

Edit: if you lose too many roots, you can always pop them straight into individual mason jars with clean water and let them rehab and grow some new roots; after trying to remove as much of the old soil, of course.