Some write they lost Data.
U cant, as the Pro version installs as a separate app! The free Version is than still on ur device if u did not delete it. Just do a backup from ur free version data (best via settings/backup via mydays server) and restore the data with the same email/backupid u used for backup, into ur pro version!!
;)
chrisamueller about MyDays X Pro, v2.4