How do I get half of my soon to be ex-husband's 401-k plan after our divorce is final? Is this a separate case after the divorce

The portion of your husband's 401-k plan that was earned during the marriage is a marital asset that is subject to equitable distribution, and should be divided euqally. However, the purpose of equitable distribution is to just divide all marital debt and assets equally, and leave the parties on as equal footing as is possible. That being said, if your husband earned $60,000 in his 401-k plan during the marriage, but walks away from the marital home leaving you with the $30,000 equity in the marital home, then your divorce is equitable. Assets and debts do not need to be split but down the middle, but the overall distribution should be equitable or fair. That being stated, your husband's 401-k plan should definitely be dealt with and distributed during your initial divorce.