Where is the PORT Mapping and Virtual server in menù router Zbtlink ZBT-WR8305RT

This is exactly what the page you posted says to do:

# in /etc/config/firewall
config redirect             
    option target 'DNAT'
    option src 'wan'
    option proto 'tcp'
    option src_dport '8099'
    option dest_port '8099'
    option name 'Zeno'
    option dest 'lan'
    option dest_ip '192.168.1.199'