File explorer and management for my ReadyNAS

Quick Question;

Is there an APP or add-on that will give me "File Explorer" functionality? I'm looking at a massive organizational project and on the 1st pass found that doing it from the standard GUI of the RN3220 is impossible as there is no true file manager integration where I can search a share for all files with an extension and then copy all to a new destination. 

I would have thought this would be pretty standard as I had this in my old Synology products but not finding it here. 

Short of running this from a client machine using search and then copy / paste, is there anything in the App family? 

Thanks