I left Jackson for a while today and my step-dad took good care of him, but he told me he had worms in his poop!

I've always checked for them moreso when I first got him so I'm thinking he got them from eating poop. I caught him yesterday eating some poop outside and it was too late to really stop him..... gross. Can I buy my own de-worming kit at Petsmart? Is it a pill or something I give to him?