To check what version of Android you have:

1.Swipe up from the home screen

2. Tap Settings

3. Tap on the Search icon

4. Type "Software information"

5. Tap "Software information"

6.Tap "Software information" again

7. The Android version that your phone is running will be displayed

Reference: 

https://www.samsung.com/uk/support/mobile-devices/how-can-i-check-what-version-of-android-i-have-on-my-device/