I just updated to the iPhone 12 a few days ago when my information was transferred to the new iPhone it did not transfer my Apple Card and I do not know how to get it back on my phone

How to add Apple Card to your Apple devices - Apple Support states:

If you have trouble adding Apple Card to a new device

1. Make sure that you're signed into the device with the same Apple ID that you used to apply for Apple Card.
2. Make sure your device has a good internet connection.
3. Make sure the Settings app and Wallet app are enabled for cellular data:
   1. Open the Settings app on your iPhone or iPad.
   2. Tap Cellular.
   3. Turn on Cellular Data.

If you need help adding Apple Card to your devices, contact Apple Support.

You are welcome.