Knowing which kind of snail you have would be ideal. If these snails don't live, you could always try again with snails from the
lfs, salt or fresh. They usually cost around 1-2.99 per snail. Some tiny ones cost around $.50.
They are not hard to keep when you know which type and have the right water for them. A 5G would be a good size tank to start with.
If they are saltwater snails, you need special Sea water salt water. Aquarium salt mixed with water is not correct.
You can get the sea water from fish stores that sell saltwater supply at around 1.25 per gallon.
If you take in an empty gallon water container or 2 to the Saltwater fish supply store they will fill them and you can use that for the water. With an air bubbler and a chunk of live rock I would recommend.
To be honest, the food snails in some stores might not survive anyway, even if they got the proper treatment.
Some of the
SW snails are meat eaters and some are more algae and some only really eat algae from rocks and glass. Knowing which one's you get dietary needs is also important.