@MojangSupport @minecraft I was on my mc world and looked for a new mountain for hours and can't find one who rare are they? How can I find them?

If this is a world you had before 1.18, you'll need to explore new chunks in order to get new world generation. If this is a new world, you might just be unlucky so far. Keep exploring and I'm sure you'll find some cool mountains! ^NS

Its a old world but I went far away from my base. How rare are they