How Do I Find Hidden Assets?

I was married for 25 years and I'm in the divorce process. During the last few years of our marriage, my husband made over $200,000 a year.  Since we've been separated for 4 years, he has had time to hide most of our assets. He says that he doesn't keep good records. He owns his own counseling business but for confidential reasons, he said that he can't show us his bookkeeping. He is the sole employee of his company.  How do I find the monetary assets that he's hidden and how do I get any money from his company? – Terrie