What if there is no option to turn Apple Cash on ?

Make sure your iPhone's region under Settings ➜ General ➜ Language & Region ➜ Region is set to the U.S.

Then you should be able to see the Apple Cash switch at the very top of Settings ➜ Wallet & Apple Pay

Also, make sure you have fulfilled all the other requirements listed in the support document you posted from.

• Be at least 18 years old and live in the United States.
• Have a compatible device with the latest iOS, iPadOS, or watchOS.
• Set up two-factor authentication for your Apple ID. 
• Sign in to iCloud with the same Apple ID on any device that you want to use to send or receive money.
• Add an eligible debit card in the Wallet app, so you can send money.