Backup the template
First, backup the blog template. (The template is your blogpsot bone)-> Enter your blog account, Click on template menu -> choose Backup / Restore
The message box will be show on, click to Download template
You'll received one file with .xml template
template-82747593275745.xml
Backup the blog data
Access below link
Choose Blogger -> and click ok
You'll received one file zip, open it this file like this: *.atom extension
You can use *.atom and *.xml to restore it later
If you have any questions or feedback, leave your comment, you can discuss about it!
Zidane