Branded typically lands on the homepage and the homepage typically only ranks for branded KWs. It is a bit more tricky if it is mixed branded (so e.g. "nike running shoes"), which technically is branded too but w/o KWs in the Google referrer it is impossible to tell whether the visitor used a mixed branded KW. If you want to look at traffic other than traffic to the HP (and conversions from HP visitors) , then you can try attribution for the main mixed branded KWs that you can see in GSC. if 40% of traffic to a page is mixed branded then you can attribute 40% of conversions generated by organic visitors to that page (or similar)