You have two options to restore TWRP to the recovery partition.
The first option, and probably the most common, is to reflash it with fastboot.
First, make sure you have fastboot installed (adb does nothing here), and then download the latest TWRP image file for your device from the official site: https://twrp.me/motorola/motorolamotog2013.html
The file you are looking for is
twrp-3.2.3-0-falcon.img and place it in a known location.
Now shutdown the device completely, and hold POWER and VOL DN to start the bootloader, then a USB cable from your phone to the computer.
Open a terminal window, and navigate to the directory containing the TWRP image file, and enter the following command:
sudo fastboot flash recovery twrp-3.2.3-0-falcon.img
Enter your password, then wait for the process to complete, and use the volume keys to select Start Recovery, and press Power to start TWRP.
The other option if you have a bootable, rooted device, is to install the official TWRP app, and install it from there.