Welcome to the forums @TungstenX!
If you know the tile ID, you can use the get_used_cells_by_id function to get all of the cell positions that contain the specific tile ID.
I'm not sure what data is in the array returned by get_used_cells_by_id
, but it should be the coordinate of the tile in the TileMap. Then from those coordinates, you can use the map_to_world function if you need to know the coordinates of the tile in world space.
To get the tile ID, you may be able to use the find_tile_by_name function in the TileSet resource attached to the TileMap.