If you've lost your registration card and need to find your registration number, here are a few steps you can follow:

1. Check Your Email/SMS: When you registered, you likely received a confirmation email or SMS containing your registration number. Search through your email inbox and SMS for any communication from the registration authority.

2. Log into the Official Portal: If your registration was done through an online portal, try logging in using the credentials you created. Once logged in, you should be able to view your registration number in your profile or registration details.

3. Contact the Support or Helpline: Look for a helpline or support email on the official website of the registration body. Provide them with your other personal details like your name, date of birth, and identification information to retrieve your registration number.

4. Visit the Office (if applicable): If it's possible, you can visit the office of the concerned authority with your identification documents, such as a government-issued ID, and request them to help you recover your registration number.

5. Check Other Documents: If your registration number was used in any application forms, acknowledgments, or admit cards, check those documents. You might find your registration number listed there.

Let us know what specific registration card you are referring to (e.g., for an exam, college, etc.), and We can guide you more specifically.