I need to count out boxes in a warehouse by using edge detection techniques; images will be taken from a 3D model of a warehouse and the propose system will be used 3 images
For a quick start I would suggest looking at those two:
These are the most widely used edge detection filters with pretty good results.
If you are starting to learn computer vision, you should also learn about typical operations in image processing and convolution.
The OpenCV library is a great library which implements many algorithms of computer vision, including the two operators mentioned above.