Q: I forgot my card number which is described in the registration .. do not tell me how I can find the card number?

Do you mean the iTunes gift card number ? If you do then it's written on the card : redeeming a card. Or do you not have a gift card ? iTunes gift cards are country-specific (they can only be used in the country in which they were issued and only onto accounts based in that country), and they aren't available in all countries, but the field on the account creation screen is optional, it doesn't have to be filled in - you can use your credit card as your payment method instead.