Changing posts archive to recipes?

Hello, I have an old recipe blog for many years. I had a simple theme and post my recipes as a normal blog post. Now i bought a food theme and i wanna change all my posts into recipes. how can i change them to recipes?

And my second question is: i want some posts to stay as posts, and some change in recipes. But they both have different category blocks. Cant i use only 1 cetagory list for both of them? Thank you.