Well, some websites like Webtoon or KissManga often have a wide range of manga titles available for online reading. Check those out to see if 'Don't Be Cruel' is there. Sometimes, you might need to search a few different sites to find it.
Well, you could check out official manga subscription services like Shonen Jump or Comixology. They often have a legal and curated collection of manga, and there's a chance 'Don't Be Cruel' might be there. Just make sure to follow the site's terms of use and respect copyright.
You might try some manga-reading websites like MangaReader or MangaPark. But be careful, some of these might not have the legal right to offer the manga for free.
I'm not sure exactly how many volumes there are. You might want to check on reliable manga databases or official publisher sites for the accurate count.