ransfer customize attributes from ShoppingCardItem to PersonWantsOrg

Hello. I need to order a multi-request resource and add a custom attribute UID_Person to the ShoppingCardItem to have the ability to select a user for request. I created similar attribute in PersonWantsOrg, but after sending an order for this request in PersonWantsOrg these fields are not automatically transferred. As i can find this transfer coding in method. How can i customize this task. Thanks