What legal document can be filed w/ the St Louis County Family Court to get an appearance before the judge on back child support

Asked in Saint Louis, MO - 10 months

She had to take her ex to court for back child support. He was ordered to pay about $400 per month for about 1 year. He made the first few payments but is now about 5 months behind. The judge warned him that if he did not make the payments on time, he would hold him in contempt. What document can my wife file with the court to get back in front of the judge to get this resolved.