Hi, your post/page content etc will not disappear or need to be rebuilt when you switch themes. No theme should ever do that and certainly none of our themes will ever do so.
Are you referring instead to the theme customizations?
If so, Exoplanet Pro comes with a handy import facility so you can import the theme customizations from Exoplanet into Exoplanet Pro with just the click of one button. See the screenshot below.
