In editing the world, enable the Caves and Cliffs option so that the world is created with a new generation of mountains.
It is very easy to find mountains. You just need to turn around after appearing in the world and go / fly forward. If your drawing range is set to a high value, then you will see the mountains immediately.
In the mountain meadows you can find a variety of flowers and bees with beehives.
In the mountains themselves, you can find a ruined portal.
Well, how about without ores in the mountains? Coal, iron and emeralds — all this can be found if you like mountaineering!