I would like to understand the process of selecting the correct tile from a scaled Surface when I have information about the number of tiles on the x and y axes, the length of the Surface, and also considering the scroll factor

Firstly, I have the following variables:

WIDTH = 640
HEIGHT = 320
MAX_COL = WIDTH // TILE_SIZE
MAX_ROW = HEIGHT // TILE_SIZE

Then, I create the base Surface with screen = pg.display.set_mode((WIDTH, HEIGHT), pg.RESIZABLE), and a dummy Surface as follows: dummy = pg.Surface([WIDTH, HEIGHT]).

Next, I create grids using some clever math and a scroll variable (which changes when I press the D button, moving everything backward):

for v in range(MAX_COL):
    # vertical / col
    pg.draw.line(dummy, (0, 0, 0), (TILE_SIZE * v - scroll_x, 0), (TILE_SIZE * v - scroll_x, HEIGHT))
    # horizontal / row
for h in range(MAX_ROW):
    pg.draw.line(dummy, (0, 0, 0), (0 - scroll_x, TILE_SIZE * h), (MAX_COL * TILE_SIZE - scroll_x, TILE_SIZE * h))

Finally, I scale it (using tw and th, calculated dimensions to maintain aspect ratio, but for now, it can be anything):

f = pg.transform.scale(s, (tw, th))
screen.blit(f, (0, 0))

Now, I want to choose a tile so that when I click it, it shows on which field I currently am. I achieve this by dividing my mouse X and Y coordinates from pg.mouse.get_pos() with the size of a scaled tile, and the result looks something like this:

Now I can go ahead and print this tile as a tuple - (2, 2)

But the problem comes when I move with my map and everything changes its position:

To select a tile like this, I would normally use my scroll variable and manipulate it (such as adding that information to the mouse x coordinate). However, it seems a bit tricky because when I scale everything, my scroll isn't accurate anymore, at least not for working with a mouse. So, I am wondering if someone knows how to maintain my coordinate system while also considering my scroll factor.