You can talk to a man in Veilistone city. His house is the first one to the left of the team galactic building.
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In veilston city behind the Pokemon center in that house that man gives you a porygon
An Up-Grade is an item that evolves the Pokemon Porygon when Porygon is traded while holding it. Porygon evolves into Porygon 2.
you can get porygon in platinum by going to velistone first, and then go to the top house on the top of the Pokemon center.Finally,you ask the man inside the house, then he will give you a porygon level 25.
Porygon
Just Evolve Porygon(1). And To Evolve Porygon(1),You Must Trade It.