where is my iTunes gift cards that were purchased

Try this:

1.

Check your spam folder of the Web version mailbox.

2.

Check the spam folder of the mail client software.

If you still need help, get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK) 

Where do you purchased?

Call the store / seller and ask them.

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