kirstey08 Yes, you can install and play all your Sims 4 content on your new computer without buying it again. Content doesn't transfer between console and PC/Mac, or between the two types of console, but owning it in the EA App means you have access to the content in Windows and macOS.
You will need to manually transfer your saves and other user data. There are a few ways to do this—external drive or USB, online filesharing service, local network if you know how to set that up—but in any case, I would suggest zipping the Sims 4 folder (or any subfolder inside) before moving it. Right-click the folder and select Compress in macOS, and once the .zip is in Windows, right-click and select Extract.
If you're wondering what data you'd want to transfer, here's a description of the contents of the user folder:
https://sims4.crinrict.com/eng/2014/09/user-files-explained/