@Chicken LittleLady   It might be best to worm your birds with a benzimidazole such as Valbazen. Valbazen kills all known types of worms a chicken can get. However, for tapeworms it's best to use a product with praziquantel to kill tapeworms, such as Equimax equine paste.
You can buy Valbazen in the link below:
https://www.valleyvet.com/ct_detail.html?pgguid=30E07949-7B6A-11D5-A192-00B0D0204AE5
The 500ml bottle will last you a long time. Dosage is 1/2ml given orally to each chicken using a syringe without a needle. Then repeat dosing again in 10 days.
There will be worm eggs in and on your soil. If your soil conditions are warm and moist most of the time, you'll have to worm your birds frequently. Chickens constantly peck the soil, in doing so they pick up worm eggs and swallow them, starting the worms lifecycle.
Frequent wormings over time stop the worms lifecycle.
It helps to rotate areas where chickens forage if they free range. If birds are penned up all or most of the time, put sand in the pens and scoop up feces often as best as you can, same for inside coops.
Yellow foamy poop can be a sign of worms. 
When you worm your birds, it's best to worm them before sunrise and make sure you withhold their feed prior to worming and 2 hours after worming. 
The chickens will be hungry and so will the worms. The worms will be at their weakest without the feed nutrients. Feed them Valbazen. Wait 2 hours after worming all your birds, then go ahead and feed your chickens a little at a time. Increase feeding them throughout the day back to normal feeding. 
Your chickens will be starving after withholding the feed. If you let them eat all they want after the 2 hours, they will gorge feed possibly causing impacted crop. 
Then repeat this procedure in 10-14 days to eliminate worms hatched from eggs missed by the first dosing.