I have a question regarding the identifier which uniquely defines an order.
In MetaTrader 4 I used the MagicNumber of the order to identify to source of the order, so, I could see the order was placed by that particular Bot.

In Dukascopy I have noticed there is a label in each order which can be retrieved by the getLabel method of the order.
This label must be unfortunately unique for each order. In MetaTrader 4 you could have the same MagicNumber for all orders placed by the Bot.

So, to write a equivalent functionality as the MagicNumber, I must write a function which parses this label for a particular value (splitting timestamp for example)?

It is the case if you want to keep that data directly in the order. Also you might consider keeping this data in comment which can get added to an order on its submission and the retrieved by IOrder.getComment().
If strategy is working with its own orders then you might as well map each order to its MagicNumber, i.e. Map<IOrder, String> magicNumbers.