You cannot find the version of the Stryd app within the app itself. Here are some ways to determine the version of the app on your phone:
On your iPhone, go to Settings --> General --> iPhone Storage. Look for Stryd, and select it. It will open another screen that will have the version information.
Open the Play Store and search for Stryd. Select "Read More" to get all the details. Scroll down. You will see the version installed on your Android phone.
Hold the Stryd icon on your home screen for a few seconds. Various options will pop up, including "App info". The app version will appear when you select "App info".