You do not need to remove the radio to find the serial number. It is retrieved through a hidden service menu on the device:
Websites like Pelock offer online calculators. You paste your ERC code, pay a small fee (usually $5-$15), and receive the unlock code immediately. toyota erc calculator hot
When the screen asks for this code, the unit is effectively "hot" or locked, rendering your maps, radio, and reversing camera (in some models) unusable. How to Get Your Toyota ERC Code You do not need to remove the radio