[Koha] duplicate biblios

[Nalisha Tamang]

Dear all,
As we have imported 26,ooo books into koha and I already had 4700 books
entered manually . as I have added 0 in front of barcode with the 4700
books e.g (02412). when i imported 26000 books it didn't replace the
existing records which has no 0 in front of barcode e.g (2400). Now when I
check the catalog it shows many duplicates. which would be 26000 books +
4700 books + duplicate biblios. Now I don't know what to do?????????
 I have attached the screenshot... please help me ASAP....
With regards,
Nalisha