The current version of theme has search by title, description and SKU (if enabled in theme options). You can find code in xstore/framework/theme-functions.php , global search results http://prntscr.com/jbxerz and Ajax search results https://prnt.sc/jbxfbq
But if you are using theme version 1.9 (too old version) I’m not sure that you have the search by SKU.
We don’t have search by brand. If you want to do any changes in search results you can do this by additional customization of the search function. If you need help with this you can contact WPKraken team.
