Hi Lily1003
I am Dave, I will help you with this.
At the top left of the dialog in your screenshot that shows the PNP driver, untick 'Show Compatible Drivers', you should then get a list of drivers, at least one of those will have the correct resolution, it does not need to be an LG driver.
Another option would be to check the LG website, to see if they provide specific drivers for that monitor.