Rather than trying to alter the information outside of iTunes manually, you need to make the adjustments from within iTunes.
Highlight the 'Unknown Album' in iTunes libraries Album pane, then do a 'Get Info', that's Command and the I key together. You will get a warning about editing information for multiple items, just click yes. Now you can fill in the Artist, Album, Composer, Genre etc. When you have finished click OK. Now you need to click on each track individually and input the relevant info there like track name for each track. Now when you look inside your itunes folder the files should no longer reside in an unknown album folder but a folder with the albums name, which may well be inside a folder with the artist name. If you select Compilation, you will find it in a folder called Compilations then artist then album name.
Hope that helps