The oldest seafloor is typically found in regions known as the "continental shelves," which are located adjacent to the continents. These regions are characterized by relatively shallow water depths and consist of the outermost edge of a continent. However, the seafloor itself constantly undergoes a process called subduction, where tectonic plates converge and the older seafloor is forced beneath younger seafloor. As a result, the oldest seafloor is usually found in areas known as subduction zones, where tectonic plates collide. Examples of such subduction zones include the western coast of South America (along the Pacific Ocean) and the eastern coast of Japan (along the Pacific Ocean).
You are most likely to find the oldest seafloor in the Pacific Ocean.
