main.dart

void main() {

  String str = "\"property_map_location\": [ \"a:2 {s:8:\"latitude\";s:9:\"13.143044\";s:9:\"longitude\";s:10:\"-61.165210\";}\" ]";

  RegExp exp = new RegExp(r's:[0-9]{1,}:"([-0-9.]+)";');

  Iterable<Match> matches = exp.allMatches(str);

  matches.toList().forEach((item) {
    print(double.parse(item[1]));
  });

}