Urdhva Mukha Svanasana (Upward Facing Dog pose) is a back extension.
Start by practicing it with your toes under. Remember the actions from Virabhadrasana I prep to lengthen the lower back while extending the fronts of the thighs.
Then, press up on the fronts of the feet into the classic pose.
To get more lift of the chest or for wrist issues, use blocks under the hands.