Missing Folder/files on "X" drive?

I backed up my files to the WD My Book WE II on “Y” drive Public but how do I know those folders/files were backed to the “X” drive download? it appears like there is nothing there. How do I check it?

thanks

JoseFern, did you find out how to check the files were been backed up or not?

Files were backed up to primary drive “Public” but there is nothing on the secondary drive (RAID 1) “Download”. How do I know files are there?