Well, we don't know exactly, but it seems they don't know what happened. They seem to think they were passed out during that period. When Peter hugged Tony Stark, we can see him mentioning that last time he was dusted he must have been passed out.
Peter: Do you remember when we were in space? And I got all dusty? I must've passed
out, 'cause I woke up, and you were gone.
Peter: But Doctor Strange was there, right? He was like, "It's been five years.
Come on, they need us!"
It seems they don't remember anything after they were dusted.
As Director Joe Russo explains,
As for Peter Parker and those who got dusted, they were basically taking a nap in which no one ages. "To those dusted people, they had no conscious in these past 5 years," Joe Russo went on. "They didn't know what happened. It's as if they had just woke up from a long sleep. The only one who was aware about how many years has passed was Doctor Strange, because he has already seen that when he was time mediating on Titan.