I need daily ohlcvi data of all futures

 
Hello, traders.
I'm developing a trading strategy using ml. For training and backtesting, I need historical ohlcvi data of all future contracts.(from all(amap) exchanges. cme, ice, nse..) I think daily data is enough.
Could someone tell me where is the best place for get data? (correct, low price, small size..)
Thanks.
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