Media files gone

I put my card into the PC; all files were there.  I copied to ITunes and pulled out of USB; now when i put card back in phone or PC the entire folder is gone and all music is gone.  How do i get back?

Are you sure you ‘copied’ them, and not ‘moved’ them? Irregardless, you should be able to ‘copy’ them back to the drive from wherever they’re stored on your hard drive. Pretty simple.