what episode straw hats reunite after 2 years

In episode 517 of the One Piece anime, titled "A New Chapter Begins - The Straw Hat Crew Reunites!", the Straw Hat Pirates reunite after two years of being separated. This marks the beginning of the Return to Sabaody Arc, where the Straw Hats have to deal with the Fake Straw Hat Crew and Pacifista. The separation occurred between Chapters 597 and 598 of the manga (Episodes 516-517 in the anime), when the Straw Hats took a two-year break and went their separate ways.