I am using an object as a prefab in my project and I have attached to it a script that does a movement. I am making some clones of it but none of them has the movement script attached to it. What could be the solution of this issue?
It sounds like you are using the prefab as a prototype, but you need to actually create an instance of the prefab in order for the script to be attached to the clone. To do this, you can drag the prefab from the project window into the scene or hierarchy, and then position and configure the instance as needed. You can also create an instance of the prefab using code at runtime by using the Instantiate method, like this:
GameObject prefab = Resources.Load("Prefabs/MyPrefab") as GameObject;
GameObject clone = Instantiate(prefab);
Once you have an instance of the prefab in the scene, you can then create clones of that instance using the Instantiate method, and the movement script will be attached to each of the clones. You can also modify the script on the prefab itself and those changes will be reflected in all of the instances and clones.