Need USB adapter for the internal hard drive used as external

When my WD5000AAKB Caviar Blue internal drive stopped working, I sent it back to WD and got a replacement. I used this drive as external drive with my PC. I mistakenly sent it back with the USB adapter (?) that was attached to it. They won’t send it back so how do I replace it and what is the proper technical name for it? I still have the USB 2.0 enclosure (box), the USB cable and the power cord. I just need the cable adapter. Where can I buy it and what should I look for? Thank you for any help on that.

Can you post the model number of the enclosure?