Sims game is not appearing in app store

It is possible that due to "regional standards" you will not be able to find a game in you country's App Store. This is normal. Not everything is available everywhere. A wide variety of meanings can be attributed to "regional standards" but if we're talking about Saudi Arabia I will go out on a limb and say that it is likely related to options and gameplay that are related to gender expression and sexual orientation. 

You might be able to bypass this by changing your address in your Apple ID information to a different country in order to get access to said county's App Store. Before doing that it's wise to consider whether you're playing with you own Apple ID or someone else's, if you have all your login credentials (email/passwords/access to inboxes, devices and phone nº for verification purposes) if your Apple ID is a minor's Apple ID, and if you can access the payment method you have on file, if any, if you're asked by Apple to enter it again. Also keep in mind that just like some things are not available in your country's store, some might not be available in the store of the country you're changing to, and some subscriptions and credits you purchased might be lost.

If you were to change your App Store country, here's a article on Apple Support on how you can do it and what consequences it might have: https://support.apple.com/en-us/HT201389