Assuming by your brief description that you are divorced with a valid child support and custody order in place, you may move the court for a contempt order. Most decrees & orders now have a provision that requires the custodial parent [sole custody situation] to notify both the court & the ex spouse of their intent to relocate out of state. You (may) have visitation rights under the order which you cannot now exercise as you don't know her location. She has the right to relocate, but not to sever your relationship with the children. A modification of the visitation order is appropriate under the circumstances. Your immediate problem is finding her to serve her with process. An investigator may have to be employed to locate her. You may also contact the CSEA to ascertain if they have an address for her, assuming she is still getting the child support. I advise obtaining an attorney, as you cannot effectively handle this matter on your own.