Copy field value from sales order to item fulfillment

Is there any way we can copy a custom field from a sales order to the same custom field on an item fulfillment record? We are trying to run a report that requires a custom field.

The field was not available on the item fulfillment until a couple of days ago. It is now on the item fulfillment. We would like to be able to get historical data using this saved search, but all item fulfillments prior to when the custom field was added do not have the data in the field.

There are 3 possible pieces of data in this field. We'll call them 1, 2, and 3. We would like to be able to update the custom field all existing item fulfillments something along the lines of if custom field on sales order=1, then 1. If custom field on sales order=2, then 2. If custom field on sales order=3, then 3.