To convert inventory back to 'Fulfilled by Merchant':
You can now view the listings on the All Inventory View page, where they will be marked as "Fulfilled by Merchant." You can begin assigning inventory to these listings at any time using the "Edit" link.
Additional resources for Fulfillment by Amazon merchants are available on the Seller Central website.
For help navigating the Seller Central website, see Seller Central Help.
Once registered, sellers can immediately begin using the Fulfillment by Amazon functionality.