if you successfully filed those returns with the IRS they should not need a second set. the notice should be specific about what they want. did you e-file and get an acceptance e-mail or did you mail it without getting proof of delivery? you may be able to go to IRS website and register to see if they have transcripts which means they got your returns However, in that case perhaps some forms weren't completed. No transcripts they never got them.
https://www.irs.gov/individuals/get-transcript
