Hello community!!! 
I have a bunch of tracks and their file names contain three digits at start. Something like this:
001 - Filename.mp3
060 - Filename.mp3
086 - Filename.mp3
...
As the title "says"... Is there any way to remove only the leading zero from filename and only if number has three digits?
Thank you for your time!!! 
You could try it with this regular expression:
$regexp(%_FILENAME%,'^0+?(\d{2})',$1)
using Convert Tag -> Tag (or an Action):

Short explanation:
Search for a zero at the start of the filename. it must be followed by 2 more numbers.
If found, keep only the two numbers (= remove the first zero).
Test and examples: regex101: build, test, and debug regex
Thank you so much!!! It's done!!! 
I think I should find some time to study regexp syntax... It's making miracles!!! 
One more question please. If I would like to do this with an action?
What have you already tried?
Create a new action, select action type "Replace with regular expression".
Fill the dialog box like this:

Worked too!!! 
And I also get an idea of the part of regexp!!! What is what...
Thank you very much for your precious time LyricsLover!!!
You really helped me here!!! 