Trouble using Arecord to record audio with new Zoom U44 interface

I bought a new Zoom U44 audio interface, and I can't figure out how to get it working with Arecord.

More specifically, I can't figure out how to choose which input on the interface I want to use. This is the command I'm using.

arecord -D "plughw:CARD=U44,DEV=0" -f cd Test.wav

It makes a recording, but it contains only silence. I assume that it's trying to record input 1, but I need to record inputs 3 and 4. I'll post the output of "arecord -L" in case it's helpful.

default:CARD=U44
U-44, USB Audio
Default Audio Device
sysdefault:CARD=U44
U-44, USB Audio
Default Audio Device
front:CARD=U44,DEV=0
U-44, USB Audio
Front speakers
surround21:CARD=U44,DEV=0
U-44, USB Audio
2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=U44,DEV=0
U-44, USB Audio
4.0 Surround output to Front and Rear speakers
surround41:CARD=U44,DEV=0
U-44, USB Audio
4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=U44,DEV=0
U-44, USB Audio
5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=U44,DEV=0
U-44, USB Audio
5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=U44,DEV=0
U-44, USB Audio
7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=U44,DEV=0
U-44, USB Audio
IEC958 (S/PDIF) Digital Audio Output
dmix:CARD=U44,DEV=0
U-44, USB Audio
Direct sample mixing device
dsnoop:CARD=U44,DEV=0
U-44, USB Audio
Direct sample snooping device
hw:CARD=U44,DEV=0
U-44, USB Audio
Direct hardware device without any conversions
plughw:CARD=U44,DEV=0
U-44, USB Audio
Hardware device with all software conversions

Thanks.