Log files are located at $FWDIR/log/ . Log files are named by the time they were closed (for example: 2020-07-06_000000.log is closed just as the day begins so it actually contain logs from 2020-07-05).
Each log has a few related files you need to copy as well, copy all the files that are named the same as the log file but with different file extensions (such as .logptr ).
If you're going to use them in the future you won't be able to see them in index mode and you'll need to either see the logs by opening a log file or re-indexing them.
Kind regards, Amir Senn