Most of the WordPress user have this question while upgrading the theme from free version to premium version.
Does all my contents loss?
Do i need to recreate my site from the beginning?
The answer is No. You can directly upload the pro theme to your WordPress site where you are using with free theme. As you are uploading the theme in the same WordPress site,your all data and contents remains same there. Deleting the theme also does not affect to your contents. Your all contents remains saved in your database. All your posts, pages and your media files will be stored in database so it is not related with the theme.
But you need to reconfigure all the settings again for your new theme. As free version and the pro version are two different themes, they both have different settings and there is many more features in the pro version than in free version. So you need to reconfigure all your contents according to Pro theme settings.