How many days had Lazarus been in the tomb when Jesus arrived?

Answer: 4

When Jesus arrived, Lazarus had already spent four days in the tomb, and Martha warned that by now he would stink.

“When Jesus arrived, He found that Lazarus had already spent four days in the tomb. “Take away the stone,” Jesus said. “Lord, by now he stinks,” said Martha, the sister of the dead man. “It has already been four days.””— John 11:17, 11:39 (BSB)