i dont think anyone is understanding my question. nvm.
I am afraid that's because you are misunderstanding something and your question doesn't make much sense.
do i use Br- ---> 3Br2 or Br- ---->Br2
Short answer - neither, as both are wrong. You should start with
and multiply it by 3 (to balance elecrons with the other half reaction), which yields
That's what you should use - it differs from both reactions you were asking about, so it was impossible to answer your question in a simple way.