I have some questions, and I'll apologize in advance if you answered any of them elsewhere in this thread.
I have owned a condo for about 10 years. It has been in pre-foreclosure for about 4 of them. My ex lived there with me but he did not pay me rent. We moved out together to a rented house and left the condo vacant for about 8 months. I left him last December and he moved back to the condo
Your ex-what? Ex-husband? Ex-boyfriend? Sounds like the latter, except for your comment about you getting "primary custody," which I guess only really implies that he's the father of the child you mentioned, but it would be helpful if you'd clarify this. I assume the condo is solely in your name. Correct?
I need him out because the bank wants it empty and broom clean. What steps should I take first?
On the assumption that title is solely in your name, you need to serve an eviction notice and file an eviction lawsuit. You can google "new jersey eviction process" and get a wealth of information (you can also probably get forms from the court's web site or court clerk's office), but you'd be far better off simply hiring an attorney who handles eviction cases.