How to convert bounding box coordinates obtained by darkflow into real world coordinates?

Question

i use realsense D435, and python 3.7, tensorflow 1.14, darkflow yolo v.2.

1. Are the camera coordinates different from the current coordinates?

2. How should the camera coordinates and the current coordinates match?

3. I want to know the center value of an object with the coordinates of the bounding box of darkflow.

I don't know much about vision. please help

Please let me know if there is a better way.