Where is the official translation of the rosary found?

There is no liturgical or official translation or text for the rosary, since it is not in liturgical books. Popular piety is regulated by the bishop of a diocese. The bishop may regulate a particular text or devotion in his diocese.

However, in the Liturgy of Hours, (an official liturgical text) for the "Commons" and antiphons in honor of the Blessed Virgin Mary, the official English translation uses the words "you" and not "thee," and "are," not "art" and "among," not "amongst."