It looks like that NBA files are just renamed ZIP files, so any utility capable of extracting ZIPs can also extract NBA. You just need to rename the extension from NBA to ZIP so programs automatically recognize it as archive.
Convert Nero BackItUp archive to WinZIP Compressed ZIP archive.
We have found 3 software records in our database eligible for .nba to .zip file format conversion.
Microsoft Windows software - convert nba to zip on Windows
Another popular file archiver and compressor
Convert from nba file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned nba to zip. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
One of the oldest and most popular shareware file archiver and data compression utility
Apple macOS / Mac OS X software - convert nba to zip on OS X
Mac version of the popular WinZip compression utility.