If your laptop uses DDR4 RAM then you can only add DDR4 RAM --- DDR3 RAM won't fit as the position of the key notch is different, the number of pins is different too.
Use crucial’s website and put in your laptop model and it will tell you what memory you should use. If you want to use multiple sticks then please buy a kit from them because adding sticks can cause problems if they’re not matched from the factory
If your laptop uses DDR4 RAM then you can only add DDR4 RAM --- DDR3 RAM won't fit as the position of the key notch is different, the number of pins is different too.