apps script convert docx to doc

function myFunction() {
  var docx = DriveApp.getFilesByName('Dummy.docx').next();
  var newDoc = Drive.newFile();
  var blob =docx.getBlob();
  var file=Drive.Files.insert(newDoc,blob,{convert:true});
  DocumentApp.openById(file.id).setName(docx.getName());  
}