This is complicated and unclear. An experienced attorney needs to know the reason why your fiance was ordered deported. Efforts can be undertaken that may prove challenging. You may not be ready for what may prove to be an emotional roller coaster. He can get married to you, where he is single, lawfully divorced, or widowed. However, your fiance may not be allowed to legally stay in the U.S. You may have to decide whether you are able or willing to leave with him/her, as well, and lawfully live in his/her home country.
An attorney will have to decide whether you should file a petition for him/her. S/He will have to decide whether s/he wants to try to re-open his removal case to get rid of the final order of deportation. This is a difficult situation. What is possible and what will be done is unclear without further information.
The above is general information, not legal advice. The above reply does not create an attorney-client relationship.