Both .nda and .nba files seems to be used as some sort of backup files by Nero BackitUp. We couldn't find information about this conversion between both file types, but if any program can work with them somehow, it would be Nero BackItUp.
Convert Nero BackItUp drive image to Nero BackItUp archive.
We found one software available in the database for this conversion.
Microsoft Windows software - convert nda to nba on Windows
As backup utility used to backup selected data, or operating system as well as hard drive
Convert from nda file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.