is there anyway to convert .CNF to .txt file?
You could open it in Notepad and save it as a txt file.
You can just rename the file in your operating system. According to this site it is stored in the same format anyway, the file extension just indicates its usage.
Why do you want to "convert" it?
A .CNF file is already an ASCII file. So you should be able to just change the extension from .cnf to .txt. But that should be unnecessary, since editors will be able to read it, as is. Just open it with (or send it to) Notepad or another editor.
Separate names with a comma.