Question about 2D to 3D,Sprite to 3D game objects

Hello good day. I got this code and this code uses sprite as chess pieces. All I want to do is to use 3D game objects instead of sprite. And I am confused on how to do that. I already got the code and it is using sprite as chess pieces. I want to use 3D models as chess piece instead of 2D sprites.

 [Serializable]
 public class PieceSet
 {
     public Sprite Pawn;
     public Sprite Bishop;
     public Sprite Knight;
     public Sprite Rook;
     public Sprite Queen;
     public Sprite King;
     public Sprite Square;
 }

 /// <summary>
 /// White pieces.
 /// </summary>
 public PieceSet WhitePieces;

 /// <summary>
 /// Black pieces.
 /// </summary>
 public PieceSet BlackPieces;






                  GameObject obj = Instantiate(SquareObj, Vector3.zero, Quaternion.identity) as GameObject;
         obj.transform.SetParent(CanvasTr, true); //set parent
         obj.transform.localPosition = new Vector3(-244 + 64 * x, 204 - 64 * y, 0); //Position it

         PieceMover pm = obj.GetComponent<PieceMover>(); //Get piece component
         pm.index = i; //Set index 
         pm.manager = this; //Set manager reference

         if ((i + y) % 2 == 0) //Change sprites according to squares
         {
             obj.GetComponent<Image>().sprite = WhitePieces.Square; //White square
         }
         else
             obj.GetComponent<Image>().sprite = BlackPieces.Square; //Black square

         //Save a square in a squares array at right index
         SquaresObj[i] = obj.transform;