Ublock Origin has 10,488,339 Users listed on it's Mozilla store-page at the moment, AdBlock Plus has 3,188,401 Users. And Firefox has surely still far more than those ~14 million users.

There was an article from Mozilla, some years ago, going more into the details about this, but I'm not sure where. Though, I found another one[1] from 2021, which starts with only one third of the users having installed an addon.

[1] https://addons.mozilla.org/blog/firefoxs-most-popular-innova...