According to the state of Montana the Constitution doesn’t say they have to make payments in gold or silver:
“The United States Constitution does not require states to pay debts in gold and silver. Additionally, there is no specific authority in the Montana Code Annotated for an agency to pay debts using gold or silver for services,”
However the actual text of the document disagrees:
No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing but gold and silver Coin a Tender in Payment of Debts; pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts, or grant any Title of Nobility.