i need help with my board manager coding ASAP

i keep getting this error code

Assets/Scripts/BoardManager.cs(71,15): error CS1525: Unexpected symbol `Vector3'

Coding:

 using UnityEngine;
 using System;
 using System.Collections.Generic;
 using Random = UnityEngine.Random;
 
 public class BoardManager : MonoBehaviour 
 {
 [Serializable]
 public class Count
 {
     public int minimum;
     public int maximum;
     
     public Count (int min, int max)
     {
         minimum = min;
         maximum = max;
     }
 }
 
 public int columns = 8;
 public int rows = 8;
 public Count wallCount = new Count (5,9);
 public Count foodCount = new Count (1,5);
 public GameObject exit;
 public GameObject[] floorTiles;
 public GameObject[] wallTiles;
 public GameObject[] foodTiles;
 public GameObject[] enemyTiles;
 public GameObject[] outerWallTiles;
 
 private Transform boardHolder;
 private List <Vector3> gridPositions = new List <Vector3> ();
 
 void InitialiseList()
 {
     gridPositions.Clear();
     
     for (int x = 1; x < columns - 1; x++)
     {
         for (int y = 1; y < rows - 1; y++)
         {
             gridPositions.Add(new Vector3(x,y,0f));
         }
     }
 }
 
 
 void BoardSetup ()
 {
     boardHolder = new GameObject ("Board").transform;
     
     for (int x = -1; x < columns + 1; x++)
     {
         for (int y = -1; y < rows + 1; y++)
         {
             GameObject toInstantiate = floorTiles[Random.Range (0, floorTiles.Length)];
             if (x == -1 || x == columns || y == -1 || y == rows)
                 toInstantiate = outerWallTiles[Random.Range (0, outerWallTiles.Length)];
             
             GameObject instance = Instantiate(toInstantiate, new Vector3 (x,y,0f), Quaternion.identity) as GameObject;
             
             instance.transform.SetParent(boardHolder);
         }
     }
 }
 
 Vector3 RandomPosition()
 {
     int randomIndex = Random.Range (0, gridPositions.Count)
 Vector3 randomPosition = gridPosition [randomIndex];
     gridPositions.RemoveAt (randomIndex);
     return randomPosition;
 }
 
 void LayoutObjectAtRandom(GameObject[] tileArray, int minimum, int maximum)
 {
     int objectCount = Random.Range (minimum, maximim + 1);
     
     for (int i = 0; i < objectCount; i++)
     {
         Vector3 randomPositions = RandomPosition();
         GameObject tileChoice = tileArray[Random.Range (0, tileArray.Length)];
         Instantiate (tileChoice, RandomPosition(), Quaternion.identity);
     }
 }
 
 public void SetupScene (int level)
 {
     BoardSetup ();
     InitialiseList ();
     LayoutObjectAtRandom (wallTiles, wallCount.minimum, wallCount.maximum);
     LayoutObjectAtRandom (foodTiles, foodCount.minimum, foodCount.maximum);
     int enemyCount = (int)Mathf.Log (level, 2f);
     LayoutObjectAtRandom (enemyTiles, enemyCount, enemyCount);
     Instantiate (exit, new Vector3 (columns - 1, rows - 1, 0f), Quaternion.identity);
     
 }

}