Unfortunately i can't do as suggested because i've to retain the same ip address so i can't work in parallel qith the old FTD, furthermore i don't have direct access to the FTD and that's why i need to have the configuration....to migrate one shoot.
You cannot do this with FTD. Manual migration is your only option here. IF you don't have access to the FTD how can you possibly migrate the config??? You can also stand up FortiGate on temp IP, then write policies/objects/interfaces/etc and then do a hot cut to the FortiGate replacing its IPs with the FTD IPs and unplug the FTD.
FTD has two packet processing engines and configuration is saved in two different ways by each of them. LINA is the ASA like engine and you can connect to LINA and get "show runn " result to migrate it like an ASA. The snort part of the config will have to be manually taken care of by editing individual policies after LINA config migration.
Note : FTD config will have application as matching criteria in access policies. Also NAT is separately configured in NAT policy in FTD. Similar settings are available in FGT policy based mode. Please look into profile based , policy based NGFW mode and central NAT options.
yes i was able only to export the objects, interfaces and nat throught the LINA, acls seem not to be correct, i'll setup the FGT with this basic settings and then i'll manually create all the policies, it is a pity because i've purchased the forticonvert service and won't be able to use it....
The Fortinet Security Fabric brings together the concepts of convergence and consolidation to provide comprehensive cybersecurity protection for all users, devices, and applications and across all network edges.