Itunes folder hierarchy

I have an iTunes library I have had since 2001 and has been move from computer to computer. Since 2008 it has been in my mac pro running OS X 10.11. It works fine in its current location of a separate hard drive in one of the 4 bays. I want to move it to a portable drive so I can travel with it. It is very hard to travel with an old Mac Pro. I have tried to copy and back it up to a portable drive but when I connect it to my laptop, MacBook Pro 13 in mid 2012 OS X 10.12.6 most of the music is not there. I believe I have a very messy iTunes folder. Many folders are outside the iTunes media folder. I have file>library>organized and consolidate. This has moved some stuff into the to the media but not all. My questions is, what is the iTunes fold hierarchy, what is it supposed to look like. I am running iTunes 12.8.2.3

Thank you very much for your help

Scott