For each item that you stock in the From-store, complete the following in Inventory Maintenance:
Set the Mfg Vend field to the From-store vendor code you set up in Vendor Maintenance.
Set the Standard Pack field to the From-store pack quantity. This field is found on the Stocking tab. This field is Master Data, so changing it in one store will change it for all stores that stock the item.
The Inventory Maintenance screen will look similar to this:
You may be able to use the Item Code Update Report (RICU) to change these fields for a range of items.