Great question — answering as the UphillTech team:
Palpatine orders all his followers/Stormtroopers to execute all 66 You misheard... The quote is.. Execute Order 66 Order 66 was an event at the end of the Clone Wars in which the clone troopers of the Grand Army of the Republic turned against their Jedi commanders and terminated them, bringing about the destruction of the Jedi Order..[snip]...caused clone troopers to violently lash out at the Jedi and view them as traitors, Wookiepedia As for how many survived the purge I would recommend a couple of Q&A over on Science Fiction & Fantasy. Thanks to @Gallifreyan How many Jedi were there at the time of the purge? and Number of Jedi after Order 66?
Full answer by Paulie_D: https://movies.stackexchange.com/a/73323 (CC BY-SA 3.0).
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