I like Valbazen myself, but it costs more, and there is a lot of it in a bottle. One dose followed in 10-14 days will get all chicken worms. Dosage is about 0.1 ml per pound. SafeGuard is good too, but to get some of the harder to treat worms, it takes 3-5 doses on consecutive days. Dosage is 1/4 ml per pound per chicken given orally. Give for 3-5 consecutive days. To treat roundworm give once and repeat in 10 days.
Some people never worm their chickens unless they have a problem, while others worm once or twice a year. In tropical regions some may do it even more often.
It can help to rotate different wormers to help prevent resistance. A vet may be of help to test fresh droppings with a fecal float to tell what what if any worms are there, and to look for an excess of coccidia. No drug treats both worms and coccidiosis. Corid (amprollium, coxoid) is the most frequently used drug for an outbreak of coccidiosis. This will help you with dosage of Corid:
https://www.backyardchickens.com/threads/updated-corid-and-amprol-amprolium-dosing.818879/