What can I do to get my belongings from my wife?

It could be helpful to speak with her attorney. You should make it clear that you will resort to Court action if she does not cooperate. In addition to requesting that a Court order that you are to have possession of those items and that she should turn over the items, you can serve a Demand for Inspection, that you will inspect her home on a certain date and time and photograph all personal property at the property. You must follow the discovery statutes to make such a request. If she fails to allow the inspection, then you can request that the Court compel the inspection.

You are in one of the most difficult situations for Family Law Court to deal with. What can the court do if you say you never got certain things, and she says she gave them to you, or you took them, or she can't find them? I believe that the most likely way to get your things back is to either get written proof that she still has the stuff (if she will admit it in a friendly email in response to you sending her some questions about what she is putting away for you), or to work with her father and "play nice" until you actually have those things in hand. If all that fails, an attorney may help to make her realize she has to turn the stuff over, but if she doesn't do it voluntarily, my experience would say that there is little chance you'll ever get it.

Do you have an attorney? If so, your attorney should talk to the other attorney and try and clear up the issue. I suppose you can get an agreement or, barring that, a court order to allow you access to the premises to look and get your stuff.

Yes, ask her attorney for a specific time to pick up the boxes and any other things. If that doesn't work go to court.