Mo. Rev. Stat. § 511.140: Judgment by default, how proceeded on to final judgment.

Whenever an interlocutory judgment shall be rendered for the plaintiff by default nihil dicit, confession, or upon an issue of law, in any suit founded upon a written instrument, or upon a judgment of any court of record, and the demand is ascertained by such instrument or the record of any such judgment, the court shall assess the damages, and final judgment shall be given thereon.