There are both countable and uncountable uses of ‘poop’ (meaning feces) but I would say that it’s more typically countable.
There is a lot of poop on the ground. (Uncountable)
The dog had a big poop.
The dog’s had three poops today. He doesn’t need to be walked again. (Countable)
Keep in mind that this is very casual English, which could be considered impolite in certain settings.