Moving iTunes library to an external drive converting to different format
I want to move entire iTunes library to an external drive. I've found several Mac 101's to help but those helps makes no sense. I should be able to move music to another drive and give iTunes the path to find it but that does not work.
All files are iTunes Plus including everything from Amazon but I want to convert everything to a mp3 or other format so all files are independent of iTunes. Lots of old music from CDs I imported and lots from iTunes as well as Amazon. I guess i could sit and burn everything to a physical cd but that would take months and hundreds and hundreds of cds. Can someone advise how I can convert these files and then move to an external drive?
I'm running mountain lion and version 10.7 of iTunes. Two external drives and 145 gigs of music. Any guidance will be most appreciated.
Thanks.
Mac mini, OS X Mountain Lion (10.8.2)