The erase process failed on Macbook Pro when trying to erase for trade in. How do I erase it?

Use Option-Command-R to launch Recovery, and try wiping and installing again.

How to reinstall macOS from macOS Recovery - Apple Support

This sequence should get you the latest release compatible with your Mac.

You need to do this procedure:

Internet/Network Recovery of El Capitan or Later on a Clean Disk

1. Restart the computer. Immediately, at or before the chime, hold down the (Command-Option-Shift-R) keys until a globe appears.
2. The Utility Menu will appear in from 5-20 minutes. Be patient.
3. Select Disk Utility and click on the Continue button.
4. When Disk Utility loads select the target drive (out-dented entry w/type and size) from the side list.
5. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.
6. Set the partition scheme to GUID.
7. Set the Format type to APFS (SSDs, only if installing Mojave or Catalina ) or Mac OS Extended, (Journaled.)
8. Provide a volume name, usually "Macintosh HD."
9. Click on the Apply button, then click on the Done button when it activates.
10. Quit Disk Utility and return to the Utility Menu.
11. Select Install OS X and click on the Continue button.

This will install the original version of macOS that came pre-installed from the factory. This is required for a trade-in. Also, see What to do before you sell, give away, or trade in your Mac.

No, whatever name you want as long as it's not the same name of any other volume. Did the error message say why the process failed? Where did the process fail? Did it fail during formatting or during macOS installation?