Notepad++ regexp ID of the sub-expressions in the double parentheses - replace

Question

I am trying to find in the Notepad++ strings like this:
'',
And convert them into this:
'',
I've made a regular expression to crop the string beginning with cards/ and ending with </a>:
(cards/)([^\s]{1,50})(([\s\.\?\!\-\,])(\w{1,50}))+(\.mp3"></a>)
Or an alternative approach:
(cards/)([^\s]{1,50})([\s\.\?\!\-\,]{0,})([^\s]{1,50})
Both work fine for search, but I can't get the replacement.
The problem is that the number of words in a sentence may vary.
And I can't get the ID of sub-expressions in the double parentheses.
The following format of replacement: \1\2\3... doesn't work, as I can't get the correct ID of the sub-expressions in the double parentheses.
I tried to google the topic, but couldn't find anything. Any advice, link or best of all a full replacement expression will be very much appreciated.

Answer 1

This will replace all spaces after /cards/ with a hyphen and lowercase the filename.
Ctrl+H
Find what: (?:href="/mp3files/cards/|\G)\K(?!\.mp3)(\S+)(?:\h+|(\.mp3))
Replace with: \L$1(?2$2:-)
CHECK Wrap around
CHECK Regular expression
Replace all
Explanation:
(?: # non capture group
href="/mp3files/cards/ # literally
| # OR
\G # restart fro last match position
) # end group
(?!\.mp3) # negative lookahead, make sure we haven't ".mp3" after this position
\K # forget all we have seen until this position
(\S+) # group 1, 1 or more non spaces
(?: # non capture group
\h+ # 1 or more horizontal spaces
| # OR
(\.mp3) # group 2, literally ".mp3"
) # end group
Replacement:
\L$1 # lowercase content of group 1
(?2 # if group 2 exists (the extension .mp3)
$2 # use it
: # else
- # put a hyphen
) # endif
Screenshot (before):
Screenshot (after):