Firewall move

This migration tool will help you in your migration from Sonic wall to Fortinet firewall.
https://www.fortinet.com/products/next-generation-firewall/forticonverter.html

You can use the migration tools to ease the process.


Update the firmware to the latest version on the Fortigate

https://www.fortinet.com/products/next-generation-firewall/forticonverter.html

I have not used the above mentioned tools.

A converter tool will not guarantee 100%  migration of your configuration between different vendor devices. If I were you, use the tool then copy both configurations on a notepad, make a comparison, adjust differences until everything is good. From my point of view, this tool is not a solution, but a good step to start and learn through the process.

I recommend considering what you intend to get out of the move. Are you trying to fix any issues or add any specific functionality with this move?

Answers to those queries may affect decisions to either:
  Try to copy your setup as-is
or
  Re design what you have to make it better

If you want it as-is, start by auditing what you have. Identify interfaces, subnets, IPs and routing info f your current firewall. try to set up the new one the same offline.
The  consider the rules/config you have in place and try to replicate those too.

Once you have it all right you can try to swap them over, knowing you can swap back if it doesnt work as expected.

Awesome suggestions!!