Personally, there is no way I would report it, as I understand the law in the US on asset forfeiture, the government can seize the money by suing the money (not you) in a civil case on “probable cause” of being obtained illegally, and then you have to prove you obtained it legally. In the OP’s case there is no way to prove you obtained it as described and it would get seized. I would proceed as follows. Bury 90 percent of it, and take $500,000 which I breakup into $50,000 bundles and leave at different lockers or safe deposit boxes. That’s my backup of the backup.
Then go speak to a Yachtie, charter a yacht and pay cash to have him sail you to the Caribbean with $20 million or however much can be fit in personal bags without arousing suspicion. Take your pick of islands, but I’ve been recommended the Turks and Caicos islands as a great place for offshore banking nowadays. Banks there can set the whole amount up in an account that won’t be reported to any other country and give you ATM and visa cards linked to that account that will work anywhere in the world.
Return to the US, then go find another Yahctie, repeat with the next sum, set it up in a different Carribean island bank. If you want to buy property with it, there’s ways from there to do that safely and plenty of consultants in the TCI (Turks and Caicos Islands) who would sort that out for you.