It is not currently possible to convert an existing community with all of its existing data into a page.

This is due to the different objectives of the two areas:

Pages tend to represent a tool for sharing information, while communities are used for collaboration within teams.
As a result, the logic in the background is different, even if the scope of functions seems identical. We thus recommend carefully considering in advance in which main category you categorize your content. 

We have set up a user community specifically to pick up on ideas like this for our future product development. Our product developers participate actively in this with the aim of gathering suggestions from our COYO users during ongoing development.