Let us pretend you have made a change to a system file, click on cpanel and clicked on backup….to backup the correct device.
Where is your backup file?
sudo find / -name mydata* /mnt/sda1/tce/mydata.tgz
Then copy that file onto usb stick etc or email it to yourself attaching mydata.tgz.
Most email clients should show a date stamp so you can keep various emails and so various backups.
Include a summary of your changes in the subject line.
sudo tar tzf /mnt/sda1/tce/mydata.tgz | less
Change sda1 to wherever the find command reports please