The graphics card cannot be replaced in a laptop. The graphics cards in laptops are very different from desktop PCs. As you can see when comparing the same models in desktop and laptop formats, their sizes are incomparable: which is normal, since your laptop has to remain portable.
To best improve the space management inside the computer, manufacturers tend to maximize space-saving solutions, and one of these is to solder the graphics card to the chassis, making it impossible to remove.