How can I get my car back from ex husband who is in possession of it. It's in my name

I am unsure if the person with the car is your current husband or ex husband. If the car was purchased during the marriage, it doesn't matter whose name is on documents; the car is marital property and only the divorce court can deal with possession. If you purchased it before getting married, in theory it's your separate property, but still in most cases the police will send you to the divorce court for an order confirming your ownership before they will assist with recovery.