Port forwarding settings are only available in Parallels Desktop Pro edition here: Parallels Desktop menu > Preferences (NOT the VM configuration) > Network.
We have checked in our end and confirmed that Parallels Desktop Business Preferences screen shows network options. Try to check if Business edition is activated or not using Parallels Desktop > About Parallels Desktop. If it shows Business edition but there is no network option in Preferences then share screenshots of Parallels Desktop About and Preferences Windows. Also, generate a problem report id and share the report number with us.