I want to use the Aqara M100 Hub as a Thread Border Router. I am able to add it to Smartthings, as well as to the Aqara app. When I try to add a Matter-over-Thread device in Smartthings, I get a prompt to choose the Thread network. I choose the one that my M100 hub is broadcasting. Smartthings then prompts to enter a “32-character network key” and I have no idea where to find this. How do I get through this stage?