You don't need one. Heed Warren Buffet's advice. Invest 90% in the S&P 500 index fund from Vanguard. Invest 10% in a federal bond money market fund from Vanguard. Spend only the interest and dividends. Pay your CPA to file your tax return. Hire a lawyer to set up a trust and will. The lawyer might also set up a Wyoming or South Dakota LLC for asset protection, but it will just hold the investment account and may hold other LLCs that own your homes or cars. It isn't complicated when you have that kind of money. Keep it simple.
The key to getting one that won't exploit you is to opt for one who handles big money. Their reputation isn't worth ruining over a few million dollars when they make that and more just doing their job. If it's from a large firm, and the person they assign to you screws you over, they will cover the loss and go after the person who skimmed from your money. You don't hire Joe's accounting to handle that money and you don't really need a complex investment plan. Just a diverse portfolio that will keep your fortune inflation proof and low risk, with enough dividends paying to find your lifestyle. Having an attorney on retainer to field money requests, protect you from shady business pitches, and deflect frivolous lawsuits is a must, as is umbrella insurance if you are going to be doing anything that's high risk. As for setting you up for the first year or so, you would have cash for that. If it were me, keep enough in HYSAs for a house and some land, including the furnishings, keep enough in a checking account for one year of expenses, with a budget, and maybe enough cash for a new car if needed, and some fun money. The rest goes straight into index funds and bonds, unless my financial advisor suggests otherwise. The kicker is how many lottery winners actually listen to their financial advisor. The guy who won the last billion dollar Powerball took home around 630 million and has spent 100 of it on mansions in California for himself and his mother, and a vintage Porsche for 250k. I'm pretty sure his financial advisor didn't get a call before all that was purchased, since he's essentially created a situation where his yearly costs will be in the millions, which can be sustainable if he's got some kick ass investments.
It depends greatly on who you are and what you want.
If you are a 60 year old with no kids and no wish to create a financial empire, throw that shit in a couple of different banks and go an enjoy your life.
People on here often assume that a person that wins the lottery wants to try to get on the forbes list or some shit.