When you export a file, you should be able to open it with the main application used to export it (not necessary the case) or with the application compatible with the file format you've exported to. If you can't open the files after the export operation has been finished, then it means you've used another format not supported by the one you want to open the files. I recommend checking the Export settings. After you click Export, a dialog window should open. Use the drop down menus to select the file type you want to use to export the data.