My Router OS is 3.30 version
I do not understand how to backup log.txt file to another pc
pl help me regarding this using by winbox
Do you want to do this manually or automatically?
Manually, you can drag and drop the file to your computer:

If you want to automate the backup, you could use email (example), FTP (example), or SSH (example) (might not work on v3.30, I don’t know).
There might be other options depending on how you want to backup the file, and where you want it to go.
I want, automatically backup log.txt file to another pc or email, please inform me details using by winbox.
you should write some script and schedule it…