i want to get to trophy garden on my pearl version to catch pichu but I cant find trophy garden on my town map?
The Trophy Garden is located on Route 212, accessed from the Pokemon Mansion. You reach it by going into the Mansion form the south, after which you head straight up into the northern/back side of the Mansion.
The trophy garden is found on Route 212 in the back garden of the Pokémon Mansion (a small building on that Route)
Leave through the back door of the Pokémon Mansion and tada! You should find an area that looks like this;
That's your trophy garden.