What is the name of pony that was with yellowship until moria?

You're likely referring to "Merry", the small, cheerful, and quick ship that served as the Straw Hats' initial vessel until the Enies Lobby arc. While the Straw Hats acquired the Thousand Sunny at Water 7, Merry was with them from the very beginning of their journey until she was unfortunately lost during the Enies Lobby arc.