I've never heard of anyone eating the skin, it would be quite tough. Just eyeballing a medium size squash I would say 4 - 5 cups cubed. Thats a tough question.
You can get butternut squash soup from cambells, its new and its in a gold carton. Its 100 calories for 1 cup and oh so tasty and filling. Its got a little kick to it but not a bad one. I eat it every day
You can also buy it frozen mashed/pureed in the frozen section of your grocers freezer.
And NO, your not ignorant, your learning
I didn't know what butternut squash was until about 5 years ago and I'm 41
Its one of my favorite veggies