I do not know where they are. She took the contents of the house with her. What can I do to find and see my children. She left no note and keeps her cell phone off

Report this to the police as a Parental Kidnapping. They may tell you that you need to first file for divorce and emergency custody of the children due to abandonment.

It is not illegal for your wife to move out and take the children, but it is illegal for her to hide the children from you (she can hide from you, but not keep the children from you).

You can also try hiring a PI to find her. If she took the contents of the house, she must have use a mover and you can possibly trace her through the mover. Talk to your neighbors to see if they remember a moving van company.

Which state or country is it in which you are located? The answer to that question will determine if "parental kidnapping" may have occurred.

A private investigator, police, or a process server will have similar questions:

Does she have friends or relatives she would go to?
Is there a history of alleged domestic violence?
Does she have bank accounts, charge cards, etc. in her name?
Did she take a vehicle with her?