iPhones
If you are using an iPhone, you can check to see if any of your apps need to be updated by going to the App Store and selecting your profile icon or picture in the top-right corner. From here, scroll down and you can see all your apps that need to be updated.
Android
To check if an Android app is up to date, open the Google Play Store, tap your profile icon (top right), select Manage apps & device, and tap Updates available to see pending updates. Apps listed here are not on the latest version; if it says "All apps up to date," you have the newest versions.