The ***USERNAME*** part is what you created in your CPanel hosting account and also the same as your prefix for SQL database install for XenForo...
The ***FORUM*** part can be deleted if XF is installed in the root of public_html folder
IE:
/home/infin/public_html/mcdownloads/downloads/
Assuming your ***USERNAME*** is infin.. change to whatever you used...
and please notice the folder is called mcdownloads... NOT microdownloads...
Hope that helps you..
Regards...