Try Maintenance>Virus Chest>right clicking>restore
If that does not work, is there any way to copy those files again. You might have to delete the contents on the USB drive then replace them.
The three alerts begs the question, wouldn't be safer to keep them in the chest and not transfer the detected files to someone else's machine let alone your own?
Dell Inspiron, Win7x64 SP1, Comodo Firewall 5.12 w/D+, MalwareBytes Free 2.1--HP Envy Win8.1x64, MalwareBytes Premium 2.1--Both systems Avast Free v2015.10.2,2218, Super Anti-Spyware, Spyware Blaster, MCShield, Unchecky, Firefox (latest build), Google Chrome (latest build) and, various browser security tools.
When you do something, do it with a purpose and do it on purpose.