。
She finally reached the North Pole.
Literal
She [topic-は] finally North-Pole [to-に] arrived.
到達する ('reach, arrive at') takes its destination with に. Slightly more formal/elevated than the everyday 着く ('arrive') — used for reaching a goal, summit, target, or notable destination. 北極 (hokkyoku, 'North Pole') is the standard term, parallel to 南極 ('South Pole') and 赤道 ('equator'). The Sino-Japanese register of 到達 fits the explorer-scale achievement; in casual speech 北極に行った ('went to the North Pole') would be the more conversational shape.