My cat has worms but the vet is closed cause it's Sunday anything I can get to help him out?

Wait for your Vet visit. Take a fresh stool sample with you so they can tell what kind of parasites. Over the counter trash is a good way to poison and kill your cat.  

Call the vet on Monday

Take your cat to the vets monday, get it flea treated and wormed

Intestinal worms are not an emergency.  Just wait till you can get an appointment.  

It takes a huge amount of worms to make an animal [or person] sick.  

Your cat has had worms for a awhile even if you're just seeing them.  This is not an emergency.

There is no such thing as a dewormer that will get rid of all worms.  Not even vets have that. 

What kind of worms are they?   Do you know?    You said nothing about what they look like.

Are they short and look like rice?  If yes, that's tapeworm.  If long and look like spaghetti, that's roundworm.   There are also may other worms that can be living inside that you don't know about.

Best advice is to take a fresh poop sample to your vet for analysis and have them give you what you need.

Yes, there are OTC dewormers.   Many include tolulene (which is toxic) and if you don't know what parasite you're treating, what's the point?

Any good pet store has deworming medicine for cats.

Some of the stuff is even made to resemble a cat treat all you got to do is throw it in with his food and the cat eats it all by himself.  You repeat the treatment in about 10 days and then repeat it 10 days after that and your cat won't have worms anymore in the meantime you have to change their litter box completely.

vets aren't the only place that sell worm tablets. Try your local pet store or even supermarkets.