A simple Google search shows this: https://www.google.com/search?q=how...0.10059j0j7&sourceid=chrome&es_sm=93&ie=UTF-8 140,000+ sites created each day That means that each year we have about 51100000 new sites launched. There's over a billion sites out there. Roughly that means 5% of all sites out there are either brand new or recent. Seems like a daunting task trying to figure out which site is new and which one isn't.
You can use Google Alerts to find new websites AFTER Google has found them - but the alerts are keyword based so you need to be looking for specific new sites.
The OP asked two separate questions How many are launched How to find them I'd respectfully suggest that answering #1 with "lots" is less helpful than answering #2