You would make your own fortune enchantment and register it. Currently, pocketmine doesn't support all of the vanilla enchantments yet. Fortune being one of them.
This is true? PHP: Enchantment::registerEnchantment(new Enchantment(self::Fortune, "Fortune", Enchantment::RARITY_COMMON, Enchantment::PICKAXE, 3));
It would be like this in PM4 PHP: use pocketmine\data\bedrock\EnchantmentIdMap;EnchantmentIdMap::getInstance()->register($id, $enchant);
Solved. Sample register code: PHP: API::register(18, new EnchantFile("EnchantName", Rarity::COMMON, ItemFlags::DIG, ItemFlags::NONE, 3));