Where can I find Palladium??

MadiiLuvhsYuh​  You could in theory use a spawner, but not all the spawners are listed in BuyDebug.  If you own World Adventures, the Metal Spawner (France) Mix High and Metal Spawner (Egypt) Mix High have the best chance of spawning palladium.  These work in any world, not just the WA destinations.  You could place a few of each on a vacant lot and wait.  Or if you have NRaas Traveler installed, it has a Force Spawners command in the menu you get when clicking on City Hall or an in-game computer.  It only forces a handful of spawners at a time, so you might need to run it a few times in a row.

If you're willing to use mods, specifically NRaas MasterController and the MC Cheats add-on, you can also search the world for palladium.  It's simpler to search the world lot (i.e. all the terrain that isn't part of a specific lot) first.  Click on a blank patch of ground, NOT on any particular lot, and select NRaas > MC > Object Info > Not Inventory, select Objects.Spawners.Metal, and if Palladium is present on the world lot, it'll be listed.  Select it to get one notification per item, in the upper-right corner of the screen.  You can click the thumbnail of the item to center the camera on it.

You can run this command for the entire world too; the downside is that it will list every single object in the world, so you'll need to scroll through a much longer list.  Click on City Hall or a computer and select NRaas > MC > Town > Object Info > Not Inventory and repeat the above.  If you want to search for the spawners, not just the metals, so you know where to look, Objects.Spawners.RockGemMetalSpawner is the category, and 5 and 6 can both produce palladium, although they also spawn other metals.  And as far as I can tell, these are NOT available in BuyDebug.

There are other mod-related interventions too, if you're getting impatient.  I can also search Moonlight Falls for you if you're not having any success on your own.

EA_QueenBee​  I'm not sure why it's hard for you to find info about Sims 3.  It's all still out there and only a Google search away.  (The Wiki spawner list is the first result; the reason it doesn't list all base game spawners under Metal is likely that many metal spawners don't appear in BuyDebug at all.)  Plus we have this whole forum with players who never abandoned Sims 3 and still know how the game works.