No. Law schools do not require that applicants have an internship or experience in a legal setting. Most legal internships are designed for law students who have already learned how to research and write like lawyer. The greatest value in legal internships for undergraduates is obtaining a realistic view of the practice of law that will help you decide whether to attend law school. You can gain this experience through talking with attorneys, shadowing attorneys, participating in mentoring programs and observing court sessions.
Most law-related internships available for undergraduates will be in government office. Search your local county's website for internship opportunities in the District Attorney's Office or the Public Defender's Office. Opportunities may also exist in other offices including those related to parole or children and youth. Here is a list of Pennsylvania county websites. You can also search at the state level in Attorney General's offices.
Use career services within your college or the Career Services Center for additional help with your internship search.