Replace card

I'm going to assume you mean the Apple Titanium credit card. If you mean something else, please edit your question with that detail.

Go into your wallet app on your iPhone. Click on the Apple credit card. In the top right corner, click on the circle with the three dots in it and scroll down until you see the section that says "Titanium Card". There is a "Request Replacement Card" option there.

See the instructions in the "Request a replacement card" section of Request and activate a titanium Apple Card - Apple Support