I just get the unsalted pumpkin seeds in the bulk nut section of the grocery store or I get a bag of organic pumpkin seeds at the healthfood store-grocery is cheaper. Then sometimes I just add it to their scratch without chopping them, or I chop them a little on a cutting board so they go further and pour some buttermilk in a pan and just throw the seeds in the buttermilk. It's a natural wormer for them.
You don't have to use buttermilk necessarily. Some just feed the chopped seeds, making sure everyone gets some. Then they give them something to make the poop out the paralyzed worms, like maybe a bunch of raisins. I even heard someone covered the raisins in DE, too, for a 1-2 punch. Either way, my Girls have never shown any signs of worms in their lives. They freerange and regularly eat earthworms and beetles, etc.
Another way is to split open an actual pumpkin and let them eat the pumpkin and the seeds. Mine dont like raw pumpkin or squash, but if I cook it, they are gluttons!