Mo. Rev. Stat. § 475.541: Registration of guardianship orders.

If a guardian has been appointed in another state and a petition for the appointment of a guardian is not pending in this state, the guardian appointed in the other state, after giving notice to the appointing court of an intent to register, may register the guardianship order in this state by filing as a foreign judgment in a court, in any appropriate county of this state, certified copies of the order and letters of office.