I am not able to add cards to the wallet

Tap Cancel, & see the following Apple articles:

Set up Apple Pay

Set up Apple Pay - Apple Support

Countries and regions that support Apple Pay

Countries and regions that support Apple Pay - Apple Support (EG)

Set up Apple Pay in Wallet on iPhone

Set up Apple Pay in Wallet on iPhone – Apple Support (UK)

See also -> About billing for Apple subscriptions and media products in India

About billing for Apple subscriptions and media products in India - Apple Support

India

•           Apple ID balance (from adding funds)

•           Net Banking (adding funds only)

•           UPI (adding funds only)

You can use / pay with your Apple ID balance, see the following Apple articles: 

Add money to your Apple ID balance

Add money to your Apple ID balance - Apple Support (IN)