You are trying to call the moveTo function on a String.
moveTO is not a String function, but fileEntry. So, first of all you need to get the Entry file from your URI.
For this, you will call window.resolveLocalFileSystemURL :
function moveFile(fileUri) {
window.resolveLocalFileSystemURL(
fileUri,
function(fileEntry){
newFileUri = cordova.file.dataDirectory + "images/";
oldFileUri = fileUri;
fileExt = "." + oldFileUri.split('.').pop();
newFileName = guid("car") + fileExt;
window.resolveLocalFileSystemURL(newFileUri,
function(dirEntry) {
fileEntry.moveTo(dirEntry, newFileName, successCallback, errorCallback);
},
errorCallback);
},
errorCallback);
}