Notepad++ replace comma if is between two double quotes

• Ctrl+H
• Find what: (?:"|\G)\d+\K,
• Replace with: LEAVE EMPTY
• CHECK Wrap around
• CHECK Regular expression
• Replace all

Explanation:

(?:"|\G)        # non capture group, double quote OR restart from last match position
\d+             # 1 or more digits
\K              # forget all we have seen until this position
,               # a comma

Screenshot (before):

Screenshot (after):