I signed up for an Apple Card, was accepted, but never received a card. I do not know my card number

Wallet app > tap the Apple Card > tap the round ... button in the upper right > tap Card Information

If you want to order the Titanium Card, that’s ordered from the same part of Wallet app in your iPhone.

You have to request a physical card. Do you have an iPhone? What device did you apply for the card through?

Settings > Wallet & Apple Pay > Apple Card > Card Info > ...

You need an iPhone to activate the Apple Card. There is a chance you won't know you card number even if you order one.