Bonnie bought a new computer and when she plugged in her external hard drive, it said it was empty. Leo says that if she still has the old system, she should plug the hard drive back in and see if the files are there. If not, then something went wrong and she didn't back up her data as she thought. That's why it's always a good idea to keep the old system around for awhile until she's moved everything over. Windows 10 should be able to see the files from that XP drive no problem.
If she dragged her files over, they should be there. If she used special software, it could be that those files are invisible or even encrypted. The key here is to make sure she has a good copy of the data when backing up files.