Not always like this and depends on model and Asus releases.
If it was in WU the file should be stored in a sub-folder of windows, if it was Asus app then its in some folder related
About ME… you should take a look at the fowling threads/tools, for better understanding:
ME Analyzer: Intel Engine Firmware Analysis Tool Discussion - Special Topics / Intel Management Engine - Win-Raid Forum (level1techs.com)
Intel (CS) Management Engine: Drivers, Firmware and Tools for (CS)ME 16+ - Special Topics / Intel Management Engine - Win-Raid Forum (level1techs.com) (Post#74 has the tool)