find out the pin numbers for the Arduino IDE for a certain board - the esp 32
An Arduino boards package with configuration for your board has constants for pins which correspond to labels on the PCB. The constants are defined in pins_arduino.h file, which is applied only if you choose the corresponding board in Tools menu. In code you should use this constants as values for your constants, like for example const uint8_t LED1_PIN = D2;.

If the boards package doesn't have the board and you use generic settings, the you can study the schematics of the board to see which PCB pin goes to which MCU pin. Usually the logical pin numbers are labeled in schematics additionally to physical pin numbers of the chip.

Note: The linked pins_arduino.h is for FireBeetle ESP32. The Beetle ESP32 is not defined in ESP32 boards package yet.

The schematics is on the Wiki page.