how do I find the log file?

Im trying to get help with a game, and I read that I need top attach a log file, but that it must be a .log file, and while theres something that seems like a log, its named "RPCS3.txt", do I need to convert that to .log or is there a different log that I should attach?

RPCS3 doesn't generate RPCS3.txt, only RPCS3.log and RPCS3.log.gz.
If you can't see extensions, you're likely using Windows and need to unhide file extensions on explorer.