Hi - my name is XXXXX XXXXX I'm a litigation attorney. Thanks for your question.
If you have a court order granting you visitation, then you have a right to enforce that order. Also, if the mother has violated the terms of that order, you have a right to charge her with contempt of court.
But, because the mother and children aren't in Oregon any longer, you're going to have to go to the state and county of their residence in order to enforce the order. However, under the Uniform Child Custody Jurisdiction Enforcement Act (UCCJEA), you have a right to take that Oregon order and enforce it in another jurisdiction.
There are some legal hoops to jump through as far as getting the order certified and transferred from Oregon to the new state, etc., but it is possible to do under this act.
The best course of action to take is to consult an attorney where they are now and try to get a petition filed for contempt and also to enforce the visitation order. If you can get this filed and her served asap, you should be able to get some results.