Determining Assets

How do you go about determining assets if the spouse is uncooperative? Situation is: seperated for over two years, but no paperwork has been filed at all. Husband left job and withdrew all of his 401K funds and now can’t determine how much he had in 401K. The employer will only tell us if so ordered by the court. I assume entitled to half the 401k funds at the time of seperation. Do I need to file a specific form with the court to get the employer to release the information? Do I need to first file for either speration or for divorce? Or file for release of 401K info. and seperation or divorce at the same time?

Also unsure whether to file for divorce now, or only seperation. Am concerned about being financially responsible for him, so want to file something to ensure against that. But have been told filing for divorce without being fully prepared (particularly as to asset information) is not a wise move.