You want Praziquantel to treat Tapeworms. Products and dosing is in the link below.
https://www.backyardchickens.com/threads/treating-tapeworms-under-construction.1220309/
To Treat Roundworms Only - Safeguard (Fenbendazole ) dose is 0.23ml per pound of weight given orally once, then repeated in 10 days.
To treat other worms that poultry can have including Roundworms, but excluding Tapeworms - Safeguard (Fenbendazole) dose is 0.23ml per pound of weight given...