Hello, Liwei Chen.
I looked at the User Guide for that extension and it doesn't show any specific configurable property for this. You might be able to adjust the RotationX, RotationY, and RotationZ properties to specify a different orientation for the model as it loads. Is this something that you have tried?
-- Craig A.
You could try to create a scene in https://threejs.org/editor/. In there, you import your model, add a Perspective Camera and save the result using the "Export Scene" option.
Then, you make the 3D Model Viewer in TWX load the exported scene. It will reuse the position of the Perspective camera that you created in the Three.js editor,