how is it obtainable????????????????

In order to get this knowledge you have to play the full main questline, you cannot get it using the simplified questline that is available for a season char. When you get to the Heidel crossroad you have to select the LEFT option, which is called "The Lamenting Head of the League of Merchants" ( https://bdocodex.com/th/quest/21004/1/ ).

You then continue to play through the questline all the way until you get to the category "[I] Apparent Ambition". The fifth quest of that category is called "Delivery of the Operation Orders" ( https://bdocodex.com/th/quest/21013/4/ ). You can then interact with the Operation Orders on the table. This gives you the knowledge for "Delphe Knights Operation Orders" ( https://bdocodex.com/th/theme/6155/ ). You then run over to Margaret and chat with her. This gives you the knowledge for "Order Delivered to Margaret".

解主線 --- 在賽林迪亞主線中分支選第一個[選擇]商人會長的苦衷，接著一直解到一個任務叫轉達作戰指令書，然後你可以和桌上的作戰指令書互動得到一個知識叫「戴爾佩騎士團作戰指令書」，然後你就可以去找瑪葛莉對話獲得「轉達給瑪葛莉的指令書」知識。

On the table of Captain