For which conference did Adolf Hitler plan 'Operation Long Jump', an assassination attempt on the three world leaders in this picture?

In 1943, Hitler planned to eliminate his enemies when they came together for the Tehran Conference. It was a planned assassinaton of the three major world leaders, Josef Stalin, Franklin Roosevelt and Wintson Churchill who had planned to meet in a neutral location, Tehran, Iran.

Called 'Operation Long Jump', it involved an advance party of six German radio operators who parachuted into Iran about 40 miles from Tehran. Their plot was discovered by a Soviet agent working undercover in a Nazi-occupied territory. Nikolai Kuznetsov got a German SS Major drunk, who then disclosed the information about the assassination plan. Working with another Soviet agent and spy, 19-year-old Gevork Vartanian and his team identified the advance party and followed them into Tehran to a safe house where they began sending information back to Berlin. Their messages were intercepted.

The German assassins were arrested and forced to contact their handlers under Soviet supervision. However, Berlin received a secret code from the arrested Germans indicating they were under surveillance. The second group of Germans never made it to Iran and the plan was thwarted.

When the war ended, the officer in charge of the assassination plot, Austrian Lieutenant Colonel Otto Skorzeny, a German Waffen SS officer denied the existence of such a plan, maintaining that he and Hilter didn't think is was feasible. Most Western scholars concede it was possible the Soviets were right about the plot.