Its been a while since I’ve used the NTBackup utility but it should be pretty straight forward.
If the backups were done within the last 10 days, you should be able to see what was backed up by looking at the reports (Tools / Reports). If the reports only show summery information, you will need to expand the cataloged information on the tape/s in question.
If the locally stored catalog files don’t exist or the tapes were from another computer, you will need to read the catalog from the tape itself. I believe when you insert an unknown tape it will prompt you to create a catalog from the tape automatically. You may have to select “Use the catalogs on the media” option first. Go to Tools / Options / General tab and make sure “Use the catalogs on the media to speed up building restore catalogs on disk” check box is enabled.