One of the dua for knowledge is rabbi zidnee ilmaa and they say if you recite this your knowledge will increase but I did not find a result. Did I do it in the wrong way? If yes then what should be the correct way to do it?

Allah’s time is always the best. Try to do the dua while in wudhu. Keep doing it from time to time and not to give up. Allah eventually make it easy for you.