Hello Deeann27,
Thank you for reaching out in Apple Support Communities. We understand you changed the passcode on your iPad Pro to a custom alphanumeric code, but that option does not appear. We'll be happy to help.
When changing the passcode to a custom alphanumeric code, the keyboard should display letters and numbers. Since, you're not seeing this layout for the keyboard, we recommend to restart your iPad Pro. Restarting your device can help resolve unexpected behavior: Restart your iPad
If that doesn't help, you may need to restore the iPad Pro to factory settings. This will help remove the passcode on your device. Here's an article with more information: Use a passcode with your iPhone, iPad, or iPod touch Specifically the section that says, "If you forgot your passcode."
Kind regards.