There are a lot of things we need to know about our chickens that are simply too small for our eyes to take in the information we need to care for them. So this is why I recommend every chicken first aid kit have a magnifying lens. You might even have one in that junk drawer you haven't pawed through in ten years.
Round worms, the white skinny long ones, have segments. (Ever see the move "Dune"?) If you don't see segments, but instead when you look through the magnifying lens you see a long smooth thing like spaghetti, it's not a worm but perhaps bits of mucous or shed intestinal lining. Or spaghetti.
But if in doubt, it's always a safe bet to go ahead and worm the flock.