Hi Abrar,
What you can do is change the dropdown to ‘Export mapping for the entire request’.
Then for the mapping, create a new JSON structure in your file explorer, and create an export mapping with that JSON structure as source. After that you can generate the needed non persistent entitities, which you can then create in the microflow calling the rest service. Select the just created export mapping in your request and add the non persistent object as input parameter.
For more information, check this documentation page.