Assaassian snails
 

Where do they come from and r they beneficial

I know the large chain stores sell them and they are native to southeast Asia, Indonesia, Malaysia, and Thailand. I like snails in my tanks so I've never had a need for them. You can also use loaches/ botias, but that might not work with all fish and tank sizes.

How would be the best way to eliminate these snails

You want to eliminate assassin snails? They don't reproduce that fast, just pick them out. Why would you want to get rid of snails anyway?

My brother lives in Florida and is over run with the trumpets and now the assassins so what he does is put a net in the tank and at the end of the day it fills up with snail s then he either uses them for fish food or dumps them ;just too many👍🌴😎

Assassin Snails
 

Au contraire, mon'amie
I started out with 5 that I had to get from the west coast because nobody seemed to sell them here at the time
When I was bringing them to the auction my population was up to 50 that I could count in my 14 Gal tank
They were like rabbits
There aren't so many these days because my water is soft enough their shells deteriorate but once I put fresh aragonite into the filter I expect more of them will survive
One would think that assassin snails would kill other assassin snails but that doesn't seem to happen
I believe they are classed as an invasive specie