PACER, Public Access to Court Electronic Records, is a online repository of court records, evidenciary, and other court documents "maintained by the Administrative Office of the U.S. Courts on behalf of the federal Judiciary". PACER is the single sign-on portal and billing account manager for Federal district, appeals, and bankruptcy courts in the United States. Individual courts maintain their own dataset, and PACER manages authentication and leverages fees for access to individual records.
Read more on Wikipedia https://en.wikipedia.org/wiki/PACER_(law)
Accounts are billed on a quarterly basis. If you account has a balance of less than $30, PACER will waive the bill.
To locate a case you need a couple pieces of information:
Case numbers formats looks something like this 2:00-cv-00084.
Case information can be found on legal search engines like Law360. While these search engine often hide most of the information behind a paywall, they expose enough to start the process on PACER.