In 3D, how can you display your camera captures on a certain surface (representing display screen) in the same viewport/scene?

Right click on the upper right corner of your viewport then choose background display then select your image or camera capture screen. If  the scene  is animated make sure you click animated background and be sure to click match animation length.

Can you elaborate please? I don't understand the question. Do you mean how to match your3D viewport with a picture taken from a camera?

in animation, if a camera placed in the scene  captures a moving subject in that scene, n i want to display this captured motion on another surface in the same scene within the same animation