I have hd custody of my 10yr old daughter. My ex and I were never married. He is threatening me for visitation only because support was raised after 10i yrs of not even calling her what should I do

Nothing you can do. He is her father. If he wants visitation, it is likely the courts will grant it. If he has never been a part of your daughter's life until now, they will, probably, restrict it to supervised visitation.