Using groups and backreferences example:
For example, to rename files "img_001.jpg", "img_002.jpg", ... to "01 - Photo.jpg", "02 - Photo.jpg", ...:
Drag in the files.
Click and choose Find & Replace.
Select “Regular expression”.
Type “img_0(\d\d)” in the “Find” box.
Type “$1 – Photo” in the “Replace” box.
Click Apply.