For converting MF to FBA, the steps are as follows:
1: Login to Seller Central
2: Go to Inventory -> Manage Inventory:
3: Select the Listed products that you need to convert:
4: Click on 'Action on *n* selected' (n, the number of selected products, is 1 in this case)
From the dropdown, click 'Convert to Fulfilled by Amazon'
5: As you follow the above steps, a new window shall open up:
6: Here, read the information carefully, and ensure you've selected the correct barcode based on your processing.
And then click 'Convert Only':
This should successfully convert your Merchant Fulfilled listed products to Fulfilled by Amazon.
Here is a.video walkthrough of the process.
