Borrowed Sims 3, still accessible w/o key, but unsure of how to purchase packs [ Edited ]

[Animephan100000]

So I have some questions I'd love help figuring out.

I borrowed the Sims 3 from my local library quite a few years ago (so back when the disc was enough and you didn't need a code to "own" the game). I recently wanted to start playing it again, and have a thesims3.com account. However, on there, it doesn't show the base game as something I own, just the one expansion pack I have (Island Paradise).
I thought of trying to purchase and potentially transfer expansion packs from Steam over to the EA app, but Steam will not let me buy the expansion packs since I don't have the base game from Steam specifically (my EA account with the sims 3 and steam are linked).
I'm unsure of what my next move should be. I've heard there's been problems with buying packs from the EA app itself, so I'm hesitant to do so through there, but also that it's potentially no longer possible to transfer the Sims 3 base game from Steam to EA if I were to make a new account to do so. Or if there's just some form of simple solution that would allow me to both get my sims 3 game "registered" through thesims3.com and buy packs from Steam and transfer to EA without needing the base game through Steam.
Any information would be extremely helpful, thank you.

[puzzlezaddict]

@Animephan100000  You'll need to buy a copy of the base game.  I would suggest waiting until Black Friday week, when Sims 3 content may be 50-60% off.  The EA App sells the "Starter Pack," which includes the base game, Late Night, and High-End Loft Stuff for the same price as one expansion, so $20 U.S. normally and as low as $8 when on sale.  In any event, it's the same price as Late Night alone, and you get a stuff pack thrown in.

Steam requires you to own the base game in Steam in order to buy any packs there.

[Animephan100000]

@puzzlezaddict Would buying the Starter Pack through the EA app cause any potential issues regarding the base game since it already exists in my game library?

[puzzlezaddict]

@Animephan100000  I thought the issue was that the base game wasn't on your account at all.  Still, it should be fine.  I have several copies of the base game on my EA account, for reasons, and I've never run into trouble trying to play on any computer.