Hello there and welcome to BYC!
You shouldn't have to worry about worms in your chickens until they are at least 8 to 10 months of age. Strike III takes care of roundworms, cecal worms, and a few others, which are the most common of worms.
Some people get poop tested at the vet to see if they have worms, others worm on a regular schedule. I have a lot of worms in my grounds so I worm once a year regardless. Most people will worm late in the year when most round worm cycles are done for the year, (when it gets too cold for the worms to reproduce)
To mix this strike III, you will mix one pound of Strike to 50 pounds of chicken feed. Mix it well so that it is evenly distributed. There should be a scoop with the bag of Strike. You can also mix one level scoop into one pound of feed if this is easier. Mix well.
I am not sure on how long you are supposed to feed this to your birds. I have heard anywhere from 1 to 6 weeks.
I prefer to use Safeguard Liquid Goat wormer. It kills pretty much everything.
Good luck!
