Private DNS Hostname

Hi I want to retain unbound logs. I have tried adding following in both unbound.conf and pi-hole.conf but i don't seem to be getting the queries and responses.

logfile: "/mnt/dns_logs/unbound.log"
    verbosity: 1

I have created unbound.log and provided user unbound access via sudo chown unbound.unbound unbound.log

What am I doing wrong here?