How do I create a GUID partition scheme on an external HD in Catalina?

hey folks, just bought the new 16" MBP and used SuperDuper to move my old hard drive contents to the new machine. Didn't go as smoothly as I'd hoped, once the restore was complete the drive wouldn't boot. After some searching I figured out how to boot into the functionality that lets you install the OS via the web. Once I did that, all was well. Great machine.

So now I'm ready to start backing this baby up. I have a Western Data external hd and when I connect it and try to use SuperDuper to copy to it, it tells me I need to convert it from APFS and that I need a GUID partition scheme. But I Disk Utility, the partition icon is greyed out and I see no other way to create a GUID partition scheme. When I click on erase, it lets me select the format of Mac OS Extended Journaled but there is no dropdown field to select scheme.

So I'm stuck. Any idea how I can make this external hard drive play nice with SuperDuper on Catalina?