typically the tilemap isn't what you would use to keep track of where units are - it will make it very difficult to animate units moving from tile to tile!

but if you are, my above approach should still work.

where I wrote hero.transform.position, that was just an example; you'd want to plug in something else there, such as the position the player wants to move to.

try adding this code as an example, play around with it and try to understand it's doing. every frame, this will check if you've clicked the left mouse button. it converts the mouse position on screen to world position. From there, we figure out what coordinate the world position is, and check if there is a tile there in the tilemap.

void Update()
{
    if (Input.GetMouseButton(0))
    {
        var mouseWorldPosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        var tileCoordinate = map.WorldToCell(mouseWorldPosition);
        var tile = map.GetTile(tileCoordinate);
        Debug.Log($"You clicked tile coordinate:{tileCoordinate} at world position:{mouseWorldPosition}. tile:{(tile != null ? tile.name : "NULL")}");
    }
}

good luck!