Im not sure what this N900 memory is. Is it a memory CARD or the internal memory? Or do you mean ROOT (/)?

Filebox is the best way to go.

Or for xterm:
sudo gainroot

and then you will be in /home
To navigate to root (/), type

cd ..

if your file is in the root. if not, from /home,

cd directory'sname
ls (to look for files and folders in that directory)

keep doing this till you find your file.
then,

ls (to look for the exact filename)
mv filename.ext /home/MyDocs/piratedpsxgames/

this will move the file to the directory you want to move it into.

EDIT:
opening the app Midnight Commander doesnt natively provide root access. you will still have to sudo gainroot through xterm to gain root access and type mc as in Midnight Commander to open it with root access.