That looks like a player's skull with a pumpkin skin. The ID for this block is
minecraft:player_head. You can set this ID as the target in Search or add it to X-Ray's ore list to easily locate them.
If some of these 'pumpkins' are placed on walls, they will have a different ID:
minecraft:player_wall_head. You could add both of these IDs to X-Ray to find them all at once. However, if you're using Search, keep in mind it can only show one ID at a time.
Hope this helps! Let me know if you have any other questions.