Collecting on a court judgment is often a lot more difficult than going through the legal process that led to the judgment. Therefore, I advise that you contact a collection attorney to help you get your money.
If the amount that J. P. Morgan owes you is large enough and the attorney feels that there is a good chance of collecting it, the attorney probably will not charge you an upfront fee to represent you. Instead, the attorney will take as payment a percentage of whatever he collects on your behalf.