You can do several things.
First of all you can have a rematch with the Elite Four, Their levels will be much higher, with the lowest level being 58, and the highest being 75.
You can also hunt down the gym leaders at certain times when they leave their gyms, and call them for rematches at certain times. Their levels vary between 50's and 60's.
You can also climb Mt. Silver to face trainer Red. His Pokemon are all in their 80's, and you will need rock climb to reach him.
Once you best him, you can get a Kanto starter from Prof. Oak, and a Hoenn starter from Steven Stone at Silph. Co. You can then go and get the red orb from Mr Pokemon and go to the embedded tower on Rt 47 to fight Groudon.
Chat with our AI personalities
no such thing
You can get Rock Climb by first getting all 16 badges. Rock climb cannot be found as an HM in the ground somewhere, but from a person. Professor Oak will give you it as a prize for getting all 16 badges.
get all 16 badges then talk to Prof. Oak
You must beat the game by getting all 8 badges then you have to beat the elite four and then the champion, Lance. After that go get all 8 Kanto badges and beat the elite four and the champion again. Then prof. Oak will see you are strong and allow you to go to mt. silver.
outside of the power plant in Kanto after you have goten all 16 gym badges.