Did I transfer all my files?

I have a SanDisk Cruzer Glide 64 GB flashdrive.

I have an IMac computer, OSX Mountain Lion,  and ITunes.

I dragged all my ITunes song files (several thousand)  to the flashdrive in order to have them backed up.

I have anoher question, (besides the 2 in my previous thread on this forum):

A few minutes after I began copying or transferring the song files from my IMac to the flashdrive, a little dialogue box said it would take about 2 hours to transfer all the 32 GBs of song files to the flashdrive. I came back 3 hours later, assuming it would be all done by then. The little dialogue box now said only about 1 GB or 1.5 GBs of 32 GBs had been copied, and it would take 2 more hours to finish copying the rest.  Then the little dialogue box disappeared, and I could not find it again. (It was not hidden behind other dialogue boxes).  I then looked in the flashdrive’s contents,  and it appears most if not all the song files had been copied to the flashdrive. Certainly way, way more than 1GB. Was this dialogue box telling me the transferring or copying of the song files was not complete,  even though it was complete? Why? Was it really completely done? How do I know if all my song files were copied to the flashdrive? Please explain the dialogue box I saw, and why it was telling me only 1 GB had been completed, which I know is not true.  

Sounds like you should be directing your questions to people on a Mac forum if you’re not sure how it works.

I will do that.

I’m no expert, but it seems that my questions are more about the SanDisk flashdrive than about ITunes. 

" it seems that my questions are more about the SanDisk flashdrive than about ITunes"

The SanDisk flashdrive didn’t write the iTunes to the drive, some app/program on your machine did.  So what app/program created the dialogue message?   IMO  You need to ask the creator of the dialogue message what it means and why it’s misleading.

By the looks of it, I don’t think it was completely transferred. Have you tried doing it again and see if it will be different?

Actually what I wrote about on the opening post was my second attempt. The same thing happened the first time I did it.

For the second time, I deleted everything in the flashdrive and then went back to square one to copy all my Itunes  song files back again to the flashdrive. Same thing happened as in the first time, a strange message via a little dialogue box saying that I had only copied a little over 1GB to the flashdrive, which is not true, and it will take about 2 hours more to finish the job.  I’m not sure, but what I think is happening is:

After the copying of all the Itunes song files to the flashdrive is completed, it starts all over and gives the message that it is just starting, and only about 1 GB has been done. I’m afraid if I do it a third time  the same thing will happen. 

Please note, that if it did not copy all the files, it copied almost all, because there are so many song files now in the flashdrive. Also I now know how to find out how many GBs have been used in my flashdrive. It is about 32.5 GBs. I believe my ITunes has about 32.5 GBs, so I most likely have all or almost all my song files in the flashdrive, since they are both about 32.5 GBs. 

By the way, I did ask this same question (see opening post) on the Apple Itunes forum, but got no response.