St. John's

... is the provincial capital of Newfoundland and Labrador.

A possible source of the confusion is that what we now know as Prince Edward Island, which was 'discovered' in 1534 by the French explorer Jacques Cartier, was named Île Saint–Jean (St. John's Island) by the French. It was known by that name until 1798 when it was renamed by the British. Today, it is known in French as Île–du–Prince–Édouard.

As far as I can ascertain, there is no place in (or on) Prince Edward Island called St. John's.