ESXi does not support automatic datastore conversions from NFS version 3 to NFS 4.1.
If you want to upgrade your NFS 3 datastore, the following options are available:
Create the NFS 4.1 datastore, and then use Storage vMotion to migrate virtual machines from the old datastore to the new one.
Use conversion methods provided by your NFS storage server. For more information, contact your storage vendor.
Unmount the NFS 3 datastore, and then mount as NFS 4.1 datastore.
https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.storage.doc/GUID-8A929FE4-1207-4CC5-A086-7016D73C328F.html