here's the law, file a motion with whatever info you have.
You can get forms at the courthouse and see what advice they offer on tracking him down to serve him with documents.
78-45a-2. Determination of paternity -- Effect -- Enforcement.
(1) Paternity may be determined upon:
(a) the petition of the mother, child, putative father, or the Office of Recovery Services; or
(b) a voluntary declaration of paternity executed in accordance with Title 78, Chapter 45e, Voluntary Declaration of Paternity Act.
(2) If paternity has been determined or has been acknowledged according to the laws of this state or any other state, the liabilities of the father may be enforced in the same or other proceedings by:
(a) the mother, child, the Office of Recovery Services, or the public authority that has furnished or may furnish the reasonable expenses of pregnancy, confinement, education, necessary support, or funeral expenses; and
(b) other persons including private agencies to the extent that they have furnished the reasonable expenses of pregnancy, confinement, education, necessary support, or funeral expenses.
(3) An adjudication of paternity or a voluntary declaration executed in accordance with Title 78, Chapter 45e, Voluntary Declaration of Paternity Act, shall be filed with the state registrar in accordance with Section 26-2-5.
(4) A party to an action under this chapter has a continuing obligation to keep the court informed of the party's current address.
Amended by Chapter 232, 1997 General