How to find MYSQL Logs for Drop Delete Record?
You must enable query logging on server as described on the official page:

https://dev.mysql.com/doc/refman/5.7/en/server-logs.html

Here general logging is the easiest approach that can be used to resolve your objective. Link shared by you shows two different methods of achieving the same. You can use following queries as root user to get what you want

SET GLOBAL log_output = 'TABLE';
SET GLOBAL general_log = 'ON';    

select event_time,user_host,argument
from mysql.general_log
where command_type='Query' and 
upper(argument) rlike '(DROP|DELETE|TRUNCATE)+';


Beware that it will fill server disk space very faster.