Isn't Keeping His End of the Agreement

The divorce is final and ED was settled in mediation.
In mediation, he agreed to hand over certain items and pay a certain amount by a given date. This date has passed and he has not done what he agreed to do.
What is my next step?

I would first send a letter to your ex, or his attorney if he has one, demanding he comply with the Order, if he still does not, file a motion for contempt.

I already sent the letter. Response included excuses, why its not his fault, and that he put the check in the mail three weeks ago.
How do I file a motion for contempt?

A motion should be filed in the court file which contains the order he is violating. The motion should specifically outline the violation of the order, and should ask that the court find him in contempt and order that he remedy the situation.
Our DIY service has a complete library of sample motions. You can learn more about the service here: www.rosen.co/diy.