How to delete rows that meet certain search criteria on Notepad++?

The version of Notepad ++, I am using is v6.9

1. Search menu -> Find... -> Mark tab -> Find what: your search text, check Bookmark Line, then Mark All. This will bookmark all the lines with the search term, you'll see the blue circles in the margin.

2. Then Search menu -> Bookmark -> Remove Bookmarked Lines. This will delete all the bookmarked lines.

Hope this helps.