Make an effort to find her current address. If you can not find her, then there is a procedure under which you apply for an order of notice when you file the divorce papers. In other words, you file for the divorce, and instead of serving her, you request an order of notice. More often than not the court will order you to publish the notice in a specific newspaper. You comply with the order of notice precisely and then file an affidavit of compliance with the court. Then, either she appears and participates, or she does not. Either way, the case will move forward and ultimately you will get the divorce.
This answer is provided for informational purposes only. Actual legal advice can only be provided in an office consultation by an attorney licensed in your jurisdiction, with experience in the area of law in which your concern lies.
You would file in your home area. Your attorney will hire a process server who can attempt to locate the spouse, and, if that fails, your attorney will know how to arrange service by publication.
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