Good news! Your Landis + Gyr meter is compatible with Powerpal.
The pulse rate to enter into the app is 1000 and you can use the rectangular mount to attach your Powerpal to your meter.
Simply attach the mounting plate over the output (marked Test) on your main consumption meter so you can line up the output through the hole in the bracket. Then gently twist your Powerpal's sensor clockwise into place.
See the image below.
Then head to https://www.powerpal.net/install and follow the instructions to complete your installation.