The sentence in active voice is:
"Jimmy ate all the pies that were at the contest."
(Note: The structure of this specific sentence may seem like it has passive elements due to "that were at the contest," but the main action "Jimmy ate" indicates that the subject (Jimmy) is performing the action. The key part about active voice is identifying who is performing the action. While it traditionally may seem to have a passive construction because of the relative clause, the primary action of eating is indeed active since Jimmy is the subject.)
The other sentences describe actions where the subject is being acted upon rather than performing the action, indicating a passive voice.