Ok apparently that's what the Splunk plugin does as well.
See "Splunk Add-on for Cisco ASA" https://splunkbase.splunk.com/app/1620/
# direction is inbound
REGEX = -30201:\s*(\S+)\s+([Ii]nbound)\s+(\S+)(?:\s+connection)?\s+(\d+)\s+for\s+([^:\s]+)\s*:\s*(?:((?:[\d+\.]+|[a-fA-F0-9]*:[a-fA-F0-9]*:[a-fA-...
It's not just NAT but also routing in your case.
For NAT this should do:
nat (inside,outside) after-auto source dynamic any interface
For routing you will need to route "inside" networks to your inside router:
route inside 192.168.10.0 255.255.255.0 172.16.0.1
route inside 192.168.20.0 255.255.255.0 172.16.0.1
route inside 192.168.30.0 255.255.255....