Sorry, I've never heard of these recipes but I'd assume that they meant standard can sizes. For your first recipe, I'd try
2 cups macaroni, cooked (there doesn't seem to be enough liquid in the other ingredients to cook dry pasta)
1 can milk - I'd use a standard 6 or 8 oz evaporated
2 cans shrimp - I'd use 2 of the smaller tuna size cans
can of mushroom soup - I'd use the standard can, not the large family size
mozzarella cheese - one can never have too much cheese
But, I'd start off with 2 cups shredded & add up to 4 cups, depending on how cheesy it looked when it was mixed in.
Now this looks like something that everyone here would eat, so maybe I'll experiment with it myself
