Which updations gives dark mode?

Dark Mode on iPhone was first introduced in iOS 13. See this Apple Developer page.

So, if you update your iPhone to iOS 13 or iOS 14, you can use dark mode.

Here is how to enable dark mode.

1. Open iPhone Settings and tap Display & Brightness.
2. Under APPEARANCE, tap Dark.

Additionally, you may also open the Control Center, press the brightness slider, and tap Dark Mode. Finally, you can even summon Siri and ask it to turn on dark mode.

Hope it helps.

You may get better and prompt responses if you may kindly provide the iPhone Model that you have and the iOS version if it is known to you and re-post.