I’ve never canned, but I think home canning requires sterilizing the glass jars of peaches, tomatoes or whatever in a big pot of boiling water. Canning tongs are used to delicately fish the jars out of the boiling water so the contents don’t cook too much.
You might find canning tongs in an old-style comprehensive hardware or “dry goods” store. Such stores are rare in big cities these days because big stores like Home Despot and Walfart have driven them out of business, but I see them in small towns.
I always see canning tongs in cooking utensil stores that cater to household gourmet cooks. If you live in a city with more than, say, 50,000 people there should be one around. Examples here in Seattle are Sur la Table, City Kitchens and Ms. Cooks.