You need to understand how to communicate with the Google Maps API. You can make a request for location information and get a response.
The request will need to be in the format defined by Google Maps API.
The response will be in the format defined by Google Maps API. There might be some options for getting this in various formats.
All the information on how to access this API, including the address is on Google's web site. You can start looking here, or there are many examples online if you search.
For example, the URL for the free geocoding service is:
Where 'XXXXXXXXX' contains the request information in the specified format
Note that this example is a free service and there is a limit on the number/frequency of requests you can make.
It may be that there is some functionality in the Blynk library to do this without going via the Arduino - but I'm just guessing. It would be worth checking because it could make things a lot easier.
Overall I don't think this is really an Arduino question, unless it is simply 'how can you interact with a website using Arduino' and I don't have any idea about that.