Add a custom field for PO number in item fulfillment from sales order.

Create a custom field that will source the PO # from Sales Order to Item Fulfillment.

• create a custom field for PO # in IF.

Go to Customization > List, Records & Fields > Transaction Body Fields > New
1. Give Label: PO #
2. Type: Free-Form Text
3. Store Value: F
4. Applies To: Item Fulfillment
5. Display Type: Disabled
In Source and Filtering Tab
Source List: Created From
Source From: PO/Check #