I have a Motorola G7 Power; carrier is Metro PCS. It is my understanding that in order to unlock the bootloader I need to get an unlock code from Motorola. Is this true? Does this mean that my device cannot be rooted unless I have this unlock code?
First check whether you phone can be unlocked: https://support.motorola.com/us/en/solution/MS87215
If yes then you need an unlock code, to get this code and unlock the boot loader follow the instructions at https://motorola-global-portal.custhelp.com/app/standalone/bootloader/unlock-your-device-a
It is not possible to root your mobile without unlocking it.