What do I have to do to get my 38 year old son to move out?

You will have to serve him with a written 30 notice to quit (leave) and then, if he still does not leave, you will have to file an unlawful detainer (eviction) action in court and get a judgment against him.

File a petition to have him evicted. Or wait until he is out drinking, box up his stuff, put the boxes out front and change the locks. Depending on where you live, that might work.

File a notice to quit and then file a complaint with the district court for eviction/re-possession. The court will set a hearing date. Your son will have 30 days after the hearing to move out. If he fails to move, the sheriff will come and remove him.

First, if your son is dangerous, call the department of child and family services or the police. If you are in danger, they will normally ask your son to leave immediately. If you are not in danger, you may have to evict your son. If he is not paying rent, the eviction rules are different and too complicated to describe in one post. If at any time you do not feel safe, call 911 immediately and ask for someone to come to your home to invite your son to leave or be arrested.