Final answer:
The first display setup menu option on the Yaesu FTM-300DR is typically the Dimmer setting for adjusting display brightness. Confirmation from the user manual is recommended due to possible updates.
Step-by-step explanation:
The first option under the display setup menu operations on the Yaesu FTM-300DR is typically the Dimmer setting, which allows the user to adjust the brightness of the display for better visibility depending on the environment. It's important to refer to the user manual for the most accurate and detailed instructions because menu options can be updated with firmware releases, and specifics can vary based on the radio's software version.