Once dry, store them in a paper envelope (not a plastic bag—mold loves plastic). Write the variety and year on it with a Sharpie. I use old notebooks, but a sandwich bag works if you poke holes.
Collect and Save Pumpkin Seeds: Pumpkin Seed Saving Guide - Smart
Keep the envelope in a cool, dark drawer. Refrigerators are too damp; basements can be too warm. Aim for 40-50°F and stable humidity. A linen closet works brilliantly.
Label them clearly. I have a jar of unlabeled seeds from two years ago. I think they’re pumpkins, but they might be squash. I’ll find out in June, or my garden will stage a mutiny.