@alexmaxzac You could try clearing IE's cache, sure. It wouldn't have anything to do with the system errors you're seeing, but maybe it would help Sims 3.
Here's a good guide to upgrading to Windows 10. I'd install using an ISO or USB stick, not the direct path through the Media Creation tool.
https://www.tenforums.com/tutorials/2267-upgrade-windows-10-a.html
It looks like if your Windows 8.1 product key is active, it may automatically grant you a Windows 10 license. Even though the upgrade program officially ended years ago, people report that it still appears to work.
When Windows 10 is installed, you'll need to install drivers too. Windows may find some for you automatically, but double-check that you have all of these:
https://pcsupport.lenovo.com/ch/en/products/desktops-and-all-in-ones/lenovo-h-series-desktops/lenovo-h50-50-desktop/downloads/driver-list
There's no harm in running them all: if that driver or a newer one is already installed, Windows should tell you, and you can move on.