This message could be posted when trying to convert either a Compositions or Audio Only export. It's stating that it cannot find the appropriate files tagged or created during the export. This is very similar to the "Where is" dialog box in Pro Tools.Verify the type of export that was done by Media Composer. Verify that when doing a Audio Only export, the Media Composer sequence should have been consolidated and exported to the external drive the Pro Tools editor has connected to his system currently. If a compositions type export was selected, the Pro Tools editor should have the original Media Composer media drive at his disposal and connected.