The Sims 3 small UI on 4k

YugiStardustITA​  You could lower the in-game resolution.  The size of the UI is tied to it, so the higher the resolution, the smaller the UI.

There's also a mod called TinyUIFix, but it's not fully compatible with certain mods, including some from NRaas, so use it at your own risk.

I see, the issue there is it makes the window smaller and there's no "full screen window" option :(

YugiStardustITA​  If you're playing in fullscreen mode, the lower resolution will still take up the entire screen, provided the aspect ratio still matches your monitor.  Otherwise, you can get black bars on the sides of the screen.  So if your monitor is 3840x2160, 1920x1080 and 2560x1440 (all 16:9) should work fine in fullscreen mode.

The Smooth Patch and the Sims 3 Settings Setter both have a Borderless mode, and Windowed Borderless Gaming is a free tool that works well with Sims 3, if you'd rather have the borderless mode functionality.

Do you reccomend the smooth patch? 
I had the game freeze a couple times it was annoying would this help?