files are missing!

I recently purchased a MacBook Pro and I am trying to transfer my files from my old Macbook using a WD My Passport for Mac portable drive. My old Macbook no longer works, but luckily I've backed up all my photos and files on this drive. I thought it would be simple to transfer all my files, but when I plug the drive into my new computer nothing happens. I can not locate my photos or files. Does anybody have experience with using this type of portable hard drive and how to transfer onto my new MacBook Pro? Thanks

We will need a bit more information to give the best answer. How did you back up the files? Drag and drop? Time Machine?

Does the hard drive show up at all on the new machine?

I backed up my old computer using an external hard drive After plugging in the external hard drive and clicking a few buttons, the hard drive backed up my files into specific categories automatically. The screen would show a bar graph with specific categories, photos, documents, etc and the percentage of space left for each categories My old computer was a macbook OSX 10.4, Tiger operating system. That computer did not have Time Machine or ICloud capabilities.