To reverse geocode (what you want to do) to determine the address of an arbitrary latitude and longitude pair is complicated. You cannot reverse geocode with App Inventor 2 Blocks without accessing an api. See this discussion for alternative solutions: Reverse GEOCODE from custom Lat Long
There are paid ways to reverse geocode, a way using the Google Map API and way’s using online converters. These are discussed in the above link.
Regards,
Steve