Hi, How many motors are used in Robotic Arm?
Depends on how it moves.
Check out some kits on google, amazon, ebay, or other sites to get a better idea.
ok, I saw on some video, that they used 3motors to pick and drop the box from one location to other.
3 is a good model. Some need to rotate the grabber so they add another. Others have more complex articulation so they use 5 or 6.
Here is a youtube channel of a talented engineer who built a large arm in his garage: Jeremy Fielding - YouTube