Found roundworm in cats watery poop

Hi I found a roundworm in one of my 6 kittens poop. They had a very wet stool nothing solid, and we aren't sure which one they are. Everyone says just deworm them, but whenever I call a vet they say they only can give it as an RX, so they would need to get seen. I showed the vet the worm and everything but they keep saying they need to see each kitten. So my question is do the ones you find at the store really work? the kittens are about 6 weeks old atm. 

Just an update, the local vet said they can sell us good quality non RX dewormer for roundworm. So looks like the kitties will be okay. 

sparkymema said:

 
Just an update, the local vet said they can sell us good quality non RX dewormer for roundworm. So looks like the kitties will be okay. 

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Good to hear.  I've never dealt with worms of any kind, thankfully.  Guess that's one advantage of living where I do, HOT and DRY.  Maybe they just don't survive long enough here to infest the animals