raneyam, what time of year will you be traveling, and what sort of budget will you have? Would you rather do all this the most economically cost-wise or are you willing to spend considerably more for, say, a private driver for the coast?
Capri can be done by ferry from Naples but how many runs a day it'll make depends on season. Season may also be a factor depending on what you want to do/see on the island. Ferries do not run directly to the Amalfi Coast from Naples. Here's the CURRENT high-season schedule to Capri from Naples:
https://www.capri.net/en/ferry-schedule
Positano, Amalfi Coast (Positano is part of that region) and Capri cannot be done in a single day trip but maybe you didn't intend to?
Editing to add: this option for the coast was suggested on one of your previous threads:
https://www.sharedtours.com
You might look into the "Amalfi Coast Full day from Sorrento" tour (by van, not boat) if there are any openings for your dates? It starts and ends in Sorrento but that would be easy - and cheap - enough by Circumvesuviana train from Naples.