If you are using Blog Designer lite version and you want to move on Pro version then you can directly do it from your dashboard as shown below.
After clicking on Upgrade to PRO Button it will redirect to codecanyon.net Blog Designer PRO plugin page where you can purchase the PRO version.
Will I lose my layout/data created in free version after upgrading to pro?
No. You will not lose your old data. After activating pro version of plugin, you will see notice for creating layout from free version of plugin.
Click on ‘Create Layout’ button. Your layout will be created in just one click.