The NVC format is a video project saved by NeroVision Express (NVE). You can open the file in NeroVision and then export it to AVI or MP4. Unfortunately, NeroVision Express isn't available on the official website. You will have to use 3rd party websites to download it and then you can perform the conversion. No converter supports the file because it's proprietary and can be opened only with the application mentioned above.
Use the websites listed in Google Search to download the application: https://goo.gl/pAIoOX