You can even make it easier than that. Launch Media Composer. With bin active, import any file - QuickTime, TIFF, whatever. Select your RAID as the destination drive. Media Composer will automatically create the Avid MediaFiles/MXF/1 folder and put the now created .mxf file in there. If you still can't find that folder on the root drive of your RAID. then click the masterclip created from the import, go to FILE menu and select "reveal file" it will open the folder containing the MXF file. Now you know where it is.
But as Nick points out, you can't drop QT wrapped DNxHD in there, all managed media is wrapped in MXF, be it DNxHD, ProRes, XDCAM, etc.
Tjere will always be a 1 folder created, it is MC's way of managing the number of files that can be managed by the operating system and will automatically create a 2, 3, when it reaches that point. That is part of the "Avid Managed" that is of benefit to you.