The original release of Office designed for Windows NT was Microsoft Office 4.2 for Windows NT.
However, Windows NT 4.0 (the operating system version you referenced, as there was no general release named "NT 4.2") came out later. The last and most recent version of Microsoft Office to support Windows NT 4.0 was Office XP, released in May 2001.
Since all of these versions are legacy software, they are no longer officially supported by Microsoft and may be difficult to acquire through official channels. You might find historical copies available for download or streaming on archives like the Internet Archive for historical or educational purposes.