Contact the store where you ordered.
Did you order from Apple?
The gift card for everything Apple -> Apple Gift Card - Apple
If so usually arrives within 1 hour.
Check your spam folder of the Web version mailbox.
Or the spam folder of the mail client software.
See the following Apple articles:
View your purchase history for the App Store, iTunes Store, and other Apple media services
View your purchase history for the App Store, iTunes Store, and other Apple media services - Apple Support
How apps, content, and subscriptions from Apple are billed
How apps, content, and subscriptions from Apple are billed - Apple Support
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
❗️See -> About Gift Card Scams
About Gift Card Scams - Official Apple Support
Get more help -> Apple Support