Save file in device internal storage using path_provider : flutter

Question

I want to save file in Device internal storage Android/Ios with path_provider. am saving file to storage with SharedPreferences if I am wring static path like /storage/emulated/0/Documents this will work on some device but not work higher version. If the file is saved using path_provider where to see this saved file?

Getting Path:

Future<String> get filePath async {
  final directory = await getApplicationDocumentsDirectory();
  return directory.path;
}

Save file to device storage:

final directory = await filePath;//directory path
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
sharedPreferences.setString(
          'Key', DateTime.now().toIso8601String());
      print('Save file to device storage');
      File filePathName = File("$directory/api_json_file.txt");
      print('Save Dir- $filePathName');
      await filePathName.writeAsString(sharedPreferences.getString('Key').toString());