You need to take care of another group of monsters to bring peace to Hyrule in Zelda: Tears of the Kingdom.
Bring Peace to Hyrule is part of the side adventures you can take in Zelda: Tears of the Kingdom to earn money and grow in combat potential.
These adventures are present all around the map of the game, and you will get to attempt them with your progression. You can take on this side adventure quite early in the game as it is found in the initial region of Tears of the Kingdom.
Make your way to the Passeri Greenbelt area in Hyrule and reach the location marked on the map below.