Replacing pool in Truenas Scale

I have a TrueNAS SCALE server as my offsite backup. In order to connect back to my main site, I use Tailscale on that machine.

Currently, my App pool is a single USB drive. I would like to change that to be 2 drives in a ZFS mirror. When the App pool was created, TrueNAS scale wouldn’t let me create any VDEV type other than stripe, so that is what the current pool is using.

How do I migrate the apps pool to be a mirror on the 2 new USBs?

If I can move the apps to the boot pool then that would be even better, the boot pool is 2 mirrored proper SSDs.

Disclaimer:
The 2 USBs are different models purchased at different times from different manufacturers, and have been through different levels of use before. Because of the above, they are unlikely to fail at the same time. I’m using USBs because 16GB is already massive overkill for tailscale and I don’t really feel like having 100+ GB for the sole purpose of installing Tailscale.