Nintex Workflow to Update list items by searching another list

I have two lists listA, listB. listA has columns of FileName , Location, Index ID. listB has Index ID, location, FileName and has data. I need to design a nintex workflow such that when an item is added to listA through some custom code already present (which I don't have access to), the Index ID, FileName of the current item that is added should be compared with the listB Index ID, FileName and the Location of List B should be populated in the Location column of listA for the matched Index ID, FileName values.