Dropepe

I just finished hoenn yesterday and went to start playing it today and i chose my starter pokemon and I went to go down route 101 (the first route of hoenn) and there is a rocket grunt named, Grunt Stella, that is blocking my route and they have 4 pokemon, the first and the only one i can get to is lvl 70. I obviously get destroyed because my treeko is only lvl 5 and then i lose and get sent back to my house in game and im just stuck. Please help me so i can continue to play the game since i cant go back to the other regions.