There is a section on your Petition for Dissolution of Marriage that addresses this issue.  Please refer back to your instructions that came with your packet.  If you are the Respondent and you wish to have your maiden name restored, the packet contains a form entitled "Request to Restore Maiden Name" that you can fill out and file with the Clerk's Office.

Once the divorce has become final and the issue of restoring your maiden name was not addressed, you will need to file for a name change with the court.

If you want to amend the birth certificate to reflect the father's last name and the parents were not married, you can file to establish paternity.  If you want to legally change the name of a minor child, use the appropriate legal form and file them with the court.