iTunes card

and the person said used I want to know where is being used

Who is the person?

See this Apple article:  If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card

If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - Apple Support

check. ⤵️

• Card is not valid
• Card has already been redeemed
• Card is not activated
• Code is unreadable
• Code must be redeemed in a different country or region
• Contact Apple Support -> Contact Apple Support.

See also -> About Gift Card Scams -> About Gift Card Scams - Official Apple Support

See also -> Terms and Conditions for Apple Gift Cards and Codes, Apple Account Associated Balance, and Content Codes

Legal - iTunes Gift Cards and Codes - Apple