Backup iTunes from hard drive to external hard drive

What is the best way to back up from hard drive to external hard drive?

When I look in my iTunes Media folder, it doesn't look like all my songs are there. I dig deeper (into further folders within the iTunes Media > Music folders) and think I find everything. How do I get them all in the main folder without screwing things up?

I did File > Library > Organize Library > Consolidate files, but that didn't re-organize them. File > Library > Organize Library > Reorganize files in the folder "iTunes Media" is greyed out and unavailable.

Am I making any sense?

I'm using Windows 10.

Any help is most appreciated.