People use the CBR file extension to designate that the file contains comic book pages in sequential order. The actual CBR file is a RAR archive. Comic book viewers can read RAR files as easily as they can read CBR files, so you do not need to convert RAR to CBR for your own use. However, to let other people know what the file contains, you might want to change CBR files to RAR files, which you can do by changing the file name.
Right-click the RAR file icon and select "Rename."
Click the RAR file name.
Delete the "rar" at the end of the file name.
Type "cbr" and press "Enter."