You're playing the wrong game. In the image that you commented I noticed that Route 10 was present, as it is in only Black/White. Route 10 was "destroyed by a landslide" in Black 2/White 2, which is why it is not present in those games. Route 19 and Route 20 didn't exist in the events of Black/White, so it's impossible to get there. You'll need to obtain a copy of Black 2/White 2 to be able to traverse those 2 routes.
Source: Your image