don't want my cat getting them...

Is your cat an outdoor cat?

If so, you can treat them, but they'll just get them again because they're eating animals outside who have tapeworm

or, you may have to call animal control

My cat is mostly indoors, but does go out for an hour or two when I get home.

So far he's ok, it's the two strays outside that have them...

you could worm them. i get treatments from my vet i don't do over the counter wormers

are they round worms or tape worms?

round worms come from having fleas

I bet they are round worms then, short white skinny, like long rice.

yep, those come from fleas.

the worm is a parasite the flea carries and gets delivered to whatever animal the flea is feeding on

if not wormed it can kill the cats you can try mixing a little raw garlic in the food but too much and the cats won't eat it