g683mj7omfm7 Please list the full specs of your Mac: everything under About This Mac including the operating system and except for the serial number.
Please also let me know if there's a reason you haven't updated to macOS Catalina (10.15) or newer. A 2017 Mac certainly can run Catalina, and some newer OSs, and that would be the simplest approach here. But if you'd rather stay on Mojave (10.14) or earlier for other reasons, I can still help get Sims 3 working.
To be clear, simply installing a newer OS won't fix the problem. What it will do is give you access to the EA App and the 64-bit version of Sims 3, which doesn't trigger the unknown error.