Deprecated Order.location_id property

Good afternoon,

I have a question about the deprecated REST property “location_id” on the Order object (Order - REST). The description suggests that

The ID of one of the locations that was assigned to fulfill the order when the order was created. Orders can have multiple fulfillment orders. These fulfillment orders can each be assigned to a different location which is responsible for fulfilling a subset of the items in an order. The Order.location_id field will only point to one of these locations. Use the FulfillmentOrder resource for up-to-date fulfillment location information.

I understand the FulfillmentOrders model and I appreciate is a one-to-many relationship between order and its FulfillmentOrders. Are there are guidelines how to make the transition between REST Order.location_id and choosing the location ID from one of the FulfillmentOrders, in terms of which FulfillmentOrder should be used? In other words, which location is being used currently to populate the deprecated Order.location_id REST property?