Lightroom 3 cannot read the NEF files from cameras that were released after Lightroom 3 support ended.
So, you'd need to upgrade to Lightroom 6 (not 7) (if your operating system supports it) OR download the free Adobe DNG Converter version 9.2 and use that to convert your NEFs to DNG, which can be read by Lightroom 3.
i upgraded to lightroom 6 and all good! Reading NEF (Raw) files from D610 and D3 cameras. Thanks.