Previous file versions (e.g. part.prt.2 > part.prt.3) can be found in the directory where the file resides. By default, Creo will retrieve the latest version. You can view all versions in the File Open dialog box by selecting Tools > All Versions from within the dialog box.
If you are referring to Trail files, these will not recreate geometry in the sense that I think you are expecting. Trail files are typically used for training purposes (and some customization purposes) but they must first be renamed from within the Windows Explorer.