How can you turn iTunes card into cash

The best way you can convert your itunes card into raw cash is by selling it out on websites that offer cash for Itunes,

Websites like Itunes Buy and Payday are Good recommendations
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See the bottom of : View your credit balance on your iPhone, iPad, iPod touch, or computer - Apple Support

You can't redeem or return iTunes or Apple Music Gift Cards or unused store credit balances for cash, except as required by law. If your jurisdiction allows for refund of redeemed gift balances, you can request a refund by contacting iTunes Store Support, selecting a support category and topic, and including the following information in your request detail:

• Your Apple ID.
• The store credit refund amount.
• Your current shipping address.

Additional information might be requested for verification purposes.