How long does a tomato worm spend in the cocoon before becoming something awesome?

I found a tomato worm on my moms tomato plant and did not have the heart to squish it. So I decided to make it a pet to show my girls how they turn into butterflies (or moths?) and it has a lovely cage and its own tomato branches.

About 2 weeks ago “David” turned into a cocoon and we have been waiting ever since. He is still alive- when I move his container the cocoon wiggles a tiny bit.

Does anyone know how long they hang out in a cocoon and what they turn into? He was a rather lovely puffy green with nice yellow and black accents.