While both New York and Pennsylvania are part of the United States, each state has its own laws and regulations regarding driver's licenses. A New York state junior license is only valid for driving within the state of New York, and it does not entitle you to drive in other states.
To drive legally in Pennsylvania, you must obtain a Pennsylvania driver's license. To do so, you will need to meet the requirements set forth by the Pennsylvania Department of Transportation (PennDOT), which may include passing a written test, a vision test, and a road test.