Bulk Rename Utility

Hi could someone please help i have audio files that i would like to batch rename for example the files are number 01,02,03 and so on i am trying to rename them with a letter after the number as in 01a,02a,03a and so on any help would be appreciated. Thank you

To suffix 'a' onto names with only numbers, can use the RegEx(1) with a 'Match' and 'Replace' like...
^(\d+)$
\1a

Thank you that was a help this is my first time using the program so please excuse my ignorance but it is only renaming one file at a time would it be possible for you to give me instruction to rename the batch
Thank for your help

To select all of the files for renaming, can either use 'Ctrl+A' or inside the menu, just use "Actions, Select All".
There is also "Actions, List, Auto-Select All Items" so this can be automatic after clicking inside of the folder-tree.
With Filters(12), you can put a checkmark in 'Subfolders' to present everything inside all of the sub-folder depths.

May i add to my last post that the file format is like this 01 David Bowie - Changes, 02 David Bowie - Diamond Dogs and i would like to have 01a David Bowie - Changes, 02a David Bowie - Diamond Dogs and so on

Thank you very much i sent the last post as you sent yours thank you so much for your help

To suffix 'a' onto numbers, when a filename begins with numbers and a space, the 'Match' and 'Replace' can be like...
^(\d+)( .+)
\1a\2

Sorry i am lost it is not a problem i will do it one by one thank you for trying

Got it sorry for being stupid i did not realise i just had to put the code you sent into the boxes i really appreciate you help, easy when you know how