In the Actions menu, the Rename 
command renames the selected files and folders.
In the Action subsection, you can choose either DOS compatible or Regular expressions rename.
DOS rename
To rename files using DOS wildcards, choose DOS compatible in the Rename dialog. In the New mask edit, enter the new name.
If multiple files or folders are selected, a base mask is computed which represents the overlap of all the names. An asterisk (*) is used to represent one or more characters, while a question mark (?) is used to represent a single character. Leave these characters alone, but change others to produce unique names for each of the selected files or folders.
Examples:
Assume that you've selected the following files to rename:
abc1.txt
abc2.txt
abc3.txt
If you enter "abc?.bak" as the new mask, the files will be renamed to:
abc1.bak
abc2.bak
abc3.bak
If you enter "xyz?.txt" as the new mask, the files will be renamed to:
xyz1.txt
xyz2.txt
xyz3.txt
Regular expression rename
To rename files using Perl compatible regular expressions, choose Regular expressions in the Rename dialog. In the Old mask edit, enter a regular expression that is matched against the original filename. In the New mask edit, enter a template used to generate a new filename.
Examples:
Assume that you've selected the following files to rename:
abc1.txt
abc2.txt
abc3.txt
If you enter "txt" as the old mask and "bak" as the new mask, the files will be renamed to:
abc1.bak
abc2.bak
abc3.bak
If you enter ".*(\d\.txt)" as the old mask and "xyz$1" as the new mask, the files will be renamed to:
xyz1.txt
xyz2.txt
xyz3.txt
