I need the hebrew name for brett

I doubt that there is one.

Hebrew does not have the BR consonent blend. There's B (Beth) and R (Resh) letters but no BR. Plus since it's not a biblical name it doesn't have a handy direct translation. The closest names in terms of sound are, well, the closest one might be Baruch or Beresh (which is more Yiddish, actually). Baruch means blessed or blessing. The ch is hard and gutteral, like in Chanukah.