In order to locate cases you will need to know their legal citation. A legal citation is a reference to the specific case, law, or law review article. The format for most legal cites is a volume number, abbreviations for the print resource, and the page number the case begins on.
Some examples:
FCC v. Pacifica Foundation, 438 U.S. 726 (1978)
Reno v. Am. Civil Liberties Union, 117 S.Ct. 2329 (1997)
Earnhardt Development Co. v. Ray, 51 S. W.2d 732
The cases are collected into volumes that are called reporter series. Some of the more common are listed below:
F. Federal Reporter
F.Supp. Federal Supplement
U.S. United States Reports
S.W. Southwestern Reporter
S.Ct. Supreme Court Reporter