How to divide 2 joints into 8 joints [iginiton gazebo] [closed]

edit

I was learning how to use Foxy with Citadel. I noticed that this generates 4 topics

 # Bridge
bridge = Node(
    package='ros_ign_bridge',
    executable='parameter_bridge',
    arguments=['/model/vehicle_blue/cmd_vel@geometry_msgs/msg/Twist@ignition.msgs.Twist',
               '/model/vehicle_blue/odometry@nav_msgs/msg/Odometry@ignition.msgs.Odometry',
               '/model/vehicle_green/cmd_vel@geometry_msgs/msg/Twist@ignition.msgs.Twist',
               '/model/vehicle_green/odometry@nav_msgs/msg/Odometry@ignition.msgs.Odometry'],
    output='screen'
)

But then I decided to add double diff drivers like this in the robot model:

  <plugin
    filename="ignition-gazebo-diff-drive-system"
    name="ignition::gazebo::systems::DiffDrive">
    <left_joint>rear_left_wheel_joint</left_joint>
    <right_joint>rear_right_wheel_joint</right_joint>
    <wheel_separation>1.25</wheel_separation>
    <wheel_radius>0.3</wheel_radius>
  </plugin>

   <plugin
    filename="ignition-gazebo-diff-drive-system"
    name="ignition::gazebo::systems::DiffDrive">
    <left_joint>front_left_wheel_joint</left_joint>
    <right_joint>front_right_wheel_joint</right_joint>
    <wheel_separation>1.25</wheel_separation>
    <wheel_radius>0.3</wheel_radius>
  </plugin>

I don't see any specific joint. Let's say, I want to control the front right wheel only. How do I do that?