OK. So the pedal that broke looked something like this?



Probably made out of plastic?

I recommend you get pedals made out of metal, like this:



or even like this:



They won't cost much more than plastic pedals, and they will last a lot longer.

Do you have a bike shop nearby? If you can, take the busted pedal with you to the shop, so you are sure to buy the right size pedal.