Vijaypat Singhania holds the world record for highest flight by a hot air balloon. It was 21km (~69000 feet). It is eleven times more than what you need.
More information about the balloon he used can be found here.
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Apparently first hot air balloon flight exceeding the requirements happened already in 1784 by Jean-François Pilâtre de Rozier. He reached 3km (~9800 feet).