I don't have a scale, about how many cups or leaves of kale should I use?

Another way you can do this is to take a quarter of your pasta and put it in a plastic bag. That's about four ounces.

Take some of the kale and put it in another plastic bag. Judge the heft of each bag, they should be about the same.

This type of recipe has some flexibility, you don't need to micromanage this to a tenth of an ounce.

Best of luck.

If one bunch of kale is one pound, then 3.5oz is just shy of a quarter of a pound, or about a quarter of a bunch of kale.