It’s pretty simple:
1 - Click on the combo .txt you want to convert on notepad++
2 - Click on Ctrl + h
3 - Copy/paste this regex in find what @[A-Za-z0-9.-]+.[A-Za-z]{2,4}\b
4 - Make sure search mode is on Regular expression https://file.coffee/u/CWWitVlQsg.png
5 - Click on replace all and that’s it now you have user:pass
Happy learning!