bbbirdieee This is the website to use:
https://www.ea.com/games/the-sims/the-sims-3/buy/addon/the-sims-3-dragon-valley
https://www.ea.com/games/the-sims/the-sims-3/buy/addon/the-sims-3-dragon-valley-gold-edition
If you buy the world from here, and you register the product code on the Sims 3 Store site, you should be fine. However, since you're playing on a Mac, please be aware that the launcher can't install Store worlds in the newest versions of macOS. Maybe you know already, but I wanted to mention that in case your other installed worlds predated an OS update. Here's the master thread:
Launcher crashes when I open the downloads tab in Sims 3 | EA Forums - 12167613
The problem is contained to Sequoia 15.4.1 and newer OSs.