I recently bought a 13" Mac Pro and an external cd drive. What cable do I need to connect the cd drive to my computer?

There is no 13” Mac Pro. Do you mean 13” MacBook Pro? That would likely need a USB-C to USB-A adapter in addition to the cable that came with the CD drive.

https://www.amazon.com/s?k=USB-c+to+usb-a+adapter

rsalmeida wrote:

what cable do I need to connect my external cd drive to my Mac Pro?

Identify the ports on your Mac - Apple Support
 https://support.apple.com/en-us/HT201736

USB-C to USB Adapter - Apple

Don't know. What connector is on your cd drive? What model/year computer?