If you mean deleted bookmarks you made in Safari, then you can't. Once deleted, they are gone.
If you've recently backed up the iPad with those bookmarks still present AND haven't made a backup (on iTunes) since, then you might be able to get them back by doing a "restore from backup" via iTunes. I've never tried that, so I don't know how/if it works.
Sorry this wasn't good news.
Marilyn