default or selected kernelversion does not have config value CONFIG_NFSD_V3.
Result is shown for kernelversion 6.9.9

NFS server support for NFS version 3

configname: CONFIG_NFSD_V3

Linux Kernel Configuration
└─>File systems
└─>Network File Systems
└─>NFS server support for NFS version 3
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
This option enables support in your system's NFS server for
version 3 of the NFS protocol (RFC 1813).

If unsure, say Y.