ScanPower doesn't automatically convert listings that are MFN when listing into Prep & Ship. You can convert the MFN items listing to FBA listing in ScanPower. Follow the below steps to do the same.
Prepare a list of all MFN SKUs (which you want to convert to FBA) into a spreadsheet as shown below:
Go to https://unity.scanpower.com/feed and upload the prepared spreadsheet in "Drag and drop or click to upload" Box.
Select only "Inventory" Checkbox and click OK button.
This will submit the feed to convert the MFN item to FBA which you can validate after a few minutes.