When your new phone/device is iOS you need to:
1) Connect to Sports-Tracker-service with your old phone if not yet connected and sync all your workouts to the web service.
2) Once the workouts are visible in www.sports-tracker.com in your profile, then just connect your new phone to the service with the same account details and your phone will automatically sync all your workouts.
Note: Deleting a workout from web will delete it from your phone and vice versa. So never delete a workout unless you're sure you don't need it anymore.