So I found out the answer. I did read the farmers’ almanac post, but apparently I missed the section on pumpkins. The answer, for those who have the same question I did is the pumpkin slices that looks like just a baking ingredient, also functions as pumpkin seeds. You craft a cutting board and knife with a wood block, stick and steel ingot, chop up the pumpkin into slices and plant those, and wait for them to grow.