Let say you have the following list of dates:

Notepad++ replace 1
01/06/2022
15/06/2022
30/12/2021
25/10/1985
01/01/2001

and you want transform them using another symbol to divide days, months and years:

Notepad++ replace 3
01-06-2022
15-06-2022
30-12-2021
25-10-1985
01-01-2001

To do this in Notepad++, you can just hit CTRL + H for Replace window and the select the following:

Notepad++ replace 2