Add array list items to firestore document

Am building a web application with Firebase Firestore as the backend. I was able to set and get values of normal data but facing difficulty with storing array data. Down below i have included an image of the structure in which I want to save that data-set I have saved that entry in the firebase console. How do I save these data in the array list into the firestore database? I'll attach the code snippet on how i save the table data to an array too Item codes and qtys saved into an array. Please do help me on this.