Question
Once the caterpillar starts to burrow in the dirt to pupate, how long does it take for him to get into the complete state of pupation?

Answer
Angie,

I'm not sure what you mean by "complete state of pupation". Pupation is more of a process rather than an end point. The whole time an insect is between the last larval instar and eclosion to the adult stage can be called pupation. Here's an article about this insect http://edis.ifas.ufl.edu/IN209 from the Univ. of Florida that includes some life cycle information.

Jack DeAngelis
http://www.livingwithbugs.com