How can I divorce a man in another state if I can't find him but need a divorce in order to re marry?

You must make a diligent search for him and at least attempt certified mail service on him at his last known address.  If the court is satisfied you have made a diligent search and could not find him, you can serve him by publishing a notice in a newspaper of adequate circulation.  If he doesn't respond to being served by publication, you can take a default judgment against him.  Beware that if he shows up later and tries to set aside the judgment, he will be given a lot of latitude to do so.  also, if he has never lived in Oklahoma or otherwise does not have significant connections with Oklahoma, the only relief the Court can give you is to dissolve the marital bonds.  No property division or other financial matters may be addressed