That's okay. This is a place to learn and share. First, the pupa (third stage) is called a chrysalis or pupa not a cocoon. Moths make cocoons.
Overcrowding can cause disease. In a 13 cup glad container, I put no more than 8 caterpillars. Make sure they have fresh food and clean out the frass (butterfly poop). As far as the number of chrysalis in a container, it depends on the size of the container. In a small net butterfly container you could put 10-20. They emerge (eclose) at different time and I'm usually letting them go when they do so they don't really bother each other as adults. Caterpillars are much more mischievous; for example, if you have eggs in a container when a new caterpillar emerges, it can crawl over and eat its room mate. Larger caterpillars may consume smaller caterpillars--not very good eye sight. Larger caterpillars may consume pupae, can't tell the difference between a leaf and a pupa (chrysalis). http://www.monarchwatch.org/rear/index.htm
Learn About Monarchshttp://faq.gardenweb.com/faq/butterfly/
The Garden Forum, Butterfly Gardening has some good information.
Have fun, I love raising butterflies and gardening for them.