using the tile map unity code example

Example 1: unity tilemap get all tiles

foreach (var position in tilemap.cellBounds.allPositionsWithin) {
            if (!tilemap.HasTile(position)) {
                continue;
            }
 
            // Tile is not empty; do stuff
        }

Example 2: unity tilemap get all tiles

public static class TilemapExtensions
{
    public static T[] GetTiles<T>(this Tilemap tilemap) where T : TileBase
    {
        List<T> tiles = new List<T>();
        
        for (int y = tilemap.origin.y; y < (tilemap.origin.y + tilemap.size.y); y++)
        {
            for (int x = tilemap.origin.x; x < (tilemap.origin.x + tilemap.size.x); x++)
            {
                T tile = tilemap.GetTile<T>(new Vector3Int(x, y, 0));
                if (tile != null)
                {
                    tiles.Add(tile);
                }
            }
        }
        return tiles.ToArray();
    }
}