Hi Varun - 

Can I ask about the FortiOS command?   In FortiOS 7.4 in my lab there doesn’t seem to be a command like you describe.   Instead you can do this to get a list of prefix-list names:

pop1-mfw01 # get router prefix-list
== b PL-1 ]
name: PL-1
pop1-mfw01 #

And then you can do this to retrieve the contents of the prefix list in the config.  Of course specifying the name PL-1 is optional - if you want to get all prefix lists just leave that off.

pop1-mfw01 # show router prefix-list PL-1
config router prefix-list
    edit "PL-1"
        set comments "Test prefix list"
        config rule
            edit 1
                set prefix 172.16.0.0 255.240.0.0
                unset ge
                unset le
            next
        end
    next
end

We don’t collect this by default, so you can add this as a custom command against Fortinet devices.

On the question about internet IP addresses being able to access your network,  does a path search not do what you need?   Like this:
 

If I have misunderstood your requirement please let me know

Best regards,

Andy​​​​​​