I need help!

I was managing an email database and thought I'd somehow deleted most of my records, so I imported them again from a backup, only to find out that the original records were there but hiddend because of a search I'd previously used.  Now I have a database full of duplicates (my original info, which I'd spent hours editing, is what I want to keep!). 

Is there a way to remove the info I most recently added in one go?