i need help how to move a certain object like of chess on certain movement
Instead of using Unity physics engine and AddForce to move the object you would make your rigidbody kinematic and modify the transform.position with new value you calculate your self based on user input (or AI or whatever) and your grid system.
If you don’t yet know how to move things around by the transform take a look in the documentation under scripting references run time classes transform Translate. For setting a new position look into Vector3 Lerp.
Grids can be done a few ways. I prefer creating vector3 positions, and placing them into an array that can be indexed, and then incremented through.
there are 2 grid packages in the asset store and a turn based toolkit.
simplest grid would be fe to round all positions to integers so you cannot place an object on 1.5 but just on 1.0 and 2.0. so you need a way to calculate the index/cell of your grid from an arbitrary position and vice versa. i have done this for hexes and it’s not trivial. so when you have few experience do what black mantis said and make some tutorials first.
if you want smooth movement bewteen your grid cells look into coroutines.