I am not licened to practice in New Jersy, but your question does not indicate the court you are proceeding in. In New Jersey state court consider using the form 10518 - New Jersey which you can find here:
This form is used for a deposition, rather than a court appearance, and includes the appropriate language for date, time, location and documents and things requested.
Disclaimer: This answer does not establish an attorney-client relationship and does not constitute legal advice. It is for general information purposes only.
Answering the particular questions you ask may be of little help to you because other questions will almost certainly arise from the answers. The rules are that technical. It sounds as though you are seeking documents only, not testimony in court. You can say this in the transmittal letter accompanying your subpoena. But you will want to get additional help.
For this reason, I strongly recommend that you hire a New Jersey family law attorney to assist you, even if it is from "behind the scenes," and you continue to represent yourself pro se. If you contact the New Jersey State Bar Association at the link below, you will find additional web links to lawyer referral service in all of New Jersey's 21 counties. For now, I have attached a second useful link from the official New Jersey courts web site to help answer some of your immediate questions concerning child support discovery.
Good luck to you in getting the assistance you need.
This response is offered for general guidance. This information should not be relied upon as specific legal advice. No attorney-client relationship is created by the exchange of emails alone.