It's a risky proposition to medicate your animals when you don't know what you're medicating for. Pancure, which is effective against nematodes / worms, is fairly safe. But with drugs like Flagyl, an anti-protozoal, you have to be very careful to get the dosage right or your snakes will overdose. Drugs like Albon, for coccidia, can also have side effects and be pretty hard on the animal. You can get pancure from a lot of feed stores, but I'm pretty sure you need a prescription to get the other drugs. You would want to get a fecal done anyway, because it's hard to chose the proper medication when you don't know what you're treating for.
If you're referring to your new snakes (sound like some kind of garter), and they are not obviously ill, it might be best to just let them live with their parasites. As long as you keep their enclose and water bowl clean, and provide an appropriate cage, furnishings, and temperatures their parasites shouldn't become an issue.
Parasites are for the most part designed to co-exist with their host. They become a problem when they reach un-natural levels. Increases in parasite load generally happen when the cage is allowed to get dirty and the animal comes into regular contact with its fecal matter or where something is wrong with the environment and the animal becomes stressed leading to a weakened immune system.
-Alice