How do I get the Apple cash card?

You have to set it up in the Wallet app. Follow the instructions in this guide published by Apple 👉 Set up Apple Cash - Apple Support

Highlights of the guide is below:

What you need

• Be at least 18 years old and live in the United States.
• Have a compatible device with the latest iOS, iPadOS, watchOS, or visionOS.
• 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.

How to set up Apple Cash

1. Open the Settings app on your iPhone.
2. Scroll down and tap Wallet & Apple Pay.
3. Turn Apple Cash on.
4. Under Payment Cards, tap Apple Cash.
5. Tap Continue, then follow the instructions on your screen

Axel F.

maybe How to apply for Apple Card - Apple Support