How do you get the stone plate on Pokemon Mystery Dungeon Explorers?

i also am searching for the stone plate, right now in eot im up to entering azuril's dream to conquer darkrai, my team is chimchar lvl 56 and piplup lvl 55 anyway just try searching the net till u find a wm code 4 it or sumthing, also i have 100 dialga, 100 ampharos and 100 kyogre, 100 groudon, 100 rayquaza, 100 tyranitar, 100 magmortar and 100 scizor...goodluck finding it ;)