My ex husband pays child support but hasn't seen my 3 year old daughter in over 2 years. My current husband is her daddy. We would like for her to have his last name. How can we do this?

You need the biological father's permission.

Your husband is not the daddy; he's the stepfather and has no legal rights as far as the child is concerned.

Would your ex consent to your present husband adopting the child? It would end the "ex's" requirement to pay child support and then your husband would be the daddy.