.3k is Advent 3B2 keyboard definition data
Key Features: .3K File Extension
What is an .3K file?
The 3k file extension is associated with Advent 3B2 software.
The 3k file stores keyboard definition data for Advent 3B2.
The Advent 3B2 seems to be obsolete product without support from developer.
This 3k file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.