Where does Origin download my DLCs? Attempting to transfer DLC content

@MamusiaTheCat  When you install the base game through Steam, Origin installs your packs into the same place as all the Steam data.  If you haven't changed the default install location in Steam, this is where the content would be:

Program Files (x86)\Steam\steamapps\common\The Sims 4

Each pack has its own folder inside that Sims 4 folder, and they're named by type of pack and release order.  (For example, Snowy Escape was the tenth expansion released, so its folder is EP10.)  It should therefore be easy to see whether Origin has downloaded all your packs.

It's not possible to add your Origin-bought packs to your Steam library.

Thank you for explaining! I did manage to find that Origin downloaded my DLCs to where Steam usually installs games a little while before your comment but I am still thankful for detailed answer. Also, where do you recommend getting my future DLCs? I really prefer sticking to one platform but it's kinda hard to do. Most of DLCs I own are on Origin (Seasons, Get Famous, Laundry Day Game Pack, Holiday Celebration Pack). I also own Cats & Dogs from Steam -34% offer for getting the game with that DLC and the following which I am not sure whether to count as actual DLCs of any sort: Awesome Animal Hats, Life of the Party, Up All Night

@MamusiaTheCat  Animal Hats, Life of the Party, and Up All Night are part of the Digital Deluxe version of Sims 4.  You can buy the DD upgrade in Origin, although it's usually cheaper to buy the DD version of the base game when it's on sale.  The content is also not strictly necessary: it's just a few items that can be easily replaced.

Personally, I'd stick with Origin because I don't want my accounts linked, I don't want to have to run two game launchers at the same time, and there are fewer ways for things to go wrong.  But to play only through Origin, you'd need to buy another copy of C&D, which is only $20 at its cheapest.  On the other hand, you could wait for a better sale—you might well see one in a year or two when Sims 4—and buy other content from Origin in the interim.  That way, you could switch to Origin-only when that sale came or when you got tired of dealing with Steam.  Or you might find that the current setup works well enough for you and you don't need to do anything.

Sale prices are the same in Origin and Steam even if the sales don't always overlap.  So if you see a new pack you want, you might need to be a bit patient, but you won't save money by purchasing through one platform over the other.

Saves can be transferred between types of installs without an issue as long as all required packs are present.

@MamusiaTheCat i need help and thought if u would be able to help bc im losing hope, so my sims stopped working and i ended up deleting it and had to download it back from steam when i originally got i from origin. for some reason my origin didnt let me download it direclty from origin. now that i downlloaded it throuht steam, none of the pack that i have bought from origin wont work. in origin it says that i have my packs installed and i also found them in file explorer in that location u gave but they wont show up in my game. also i tried to see them in steam but i dont have them in steam so idk what to do

@veeramariiaaa  Clear Origin's cache:

https://help.ea.com/en/help/faq/clear-cache-to-fix-problems-with-your-games/

Then try to download the packs from Origin.  Even with a base game installed from Steam, Origin should allow you to download any packs you've bought there.

hi i installed sims 4 base game on steam because my sims 4 wasnt working on the new ea app but i ran it and it didnt have my dlc so i went baack to ea app reinstalled sims 4 and im missing all of my dlc packs that i bought and ive tried to reinstall them but i dont  know how since i dont know how to on the ea app it says they are in the library but when i launch it i dont have any access to my pack please help

@Miss_Tinkleton  Please do a clean uninstall and reinstall of Sims 4 and the EA App.  Start with Sims 4:

• Put aside your Sims 4 folder in Documents\Electronic Arts and rename it to something that doesn't include the words "Sims 4."
• Download Revo Uninstaller (the free version is fine) from here.
• Launch Revo, select Sims 4 from the list, and click Uninstall.
• Once the game is uninstalled, select "Moderate" under "scanning modes," and click Scan.
• Review the list, in case there's something you want to save; otherwise, click Select All, and then Delete.
• Close Revo, and restart your computer.

Uninstall the EA App the same way.  I don't have instructions for it at the moment, but it should be straightforward.

Restart your computer, install the EA App, and download Sims 4 from there.  Don't involve Steam at all.

Additionally, if you have the Sims 4 CAS Demo installed, please rename its folder before reinstalling Sims 4.  The CAS Demo would likely be here:

Program Fiels (x86)\Origin Games\The Sims 4 Create a Sim Demo