How to insert data in custom coloumn in sales_creditmemo_item table from SalesControllerAdminhtmlOrderCreditmemoSave.php? magento 2

Basically I manually created custom column in my database named as item_number Now I want to insert data into this column from appcodecompanySalesControllerAdminhtmlOrderCreditmemoSave.php and the purpose of this column is that it will store the item number of each item. As sales_creditmemo_item inserts data or stores data of each item of the order so I would like to add item Number of that item into item_number column in sales_creditmemo_item table.I have been referring to appcodecompanySalesModelOrderCreditMemoItem.php, vendormagentomodule-salesControllerAdminhtmlOrderCreditmemoLoader.php and appcodecompanySalesApiDataCreditMemoItemInterface.php but it is confusing me to implement. But It would be really helpful for me to continue my learning about magento 2 backend concepts if anyone could point any suggestion or advice. Thanks and cheers