Nissan Terrano ATF

Gud day, would like to ask you folks on what type of ATF should i replace on my terrano. its a 1991 Japanese import R3m, TD27 4 speed auto trans. read on a website that when your auto trans fluid turns amber or brown in color, it needs to be replaced. just checked on my car and it turned out to be amber in color. both dexron 2 and dexron 3 types of atf are availabe here. would like to ask also the difference between dexron 2 and dexron 3 and if i can use the dexron 3 type. :-)