One large squash should easily yeild 6 cups of meat. Take a look at the typical seed well of a butternut squash. You should be able to guage the size you'll need by that:
To cook one, slice it in half lengthwise with a sturdy knife, scoop out the seeds, place cut side down on a baking sheet and bake at 350 for about an hour, or until squash is tender, then scoop out the meat and puree it in a blender or food processor. Alternatively, you can pierce the whole squash with a fork several times, place it in a microwave oven and cook on high about 15 minutes, or until tender. Then slice it in half, remove the seeds and puree the meat.
I don't trust anyone who needs a recipe to make tossed salad.