The connections of the OLED with the Arduino are as follows:

Connect CS of SD card module to pin 10 of Arduino



Connect MOSI of SD card module to pin 11 of Arduino



Connect MISO of SD card module to pin 12 of Arduino



Connect SCK of SD card module to pin 13 of Arduino



Connect VCC of SD card module to 5V pin of Arduino



Connect GND of SD card module to GND pin of Arduino



After that, connect the DS3231 module with the Arduino. The DS3231 module works with the Arduino through the I2C communication. The pins for I2C communication on the Arduino are SDA and SCL.

Connect the DS3231 module with the Arduino as follows:

Connect GND of DS3231 to GND pin of Arduino



Connect VCC of DS3231 to 5V pin of Arduino



Connect SDA of OLED to A4 pin of Arduino



Connect SCL of OLED to A5 pin of Arduino



In the end, connect the LM35 sensor with the Arduino. Connect the left pin of LM35 to 5V of Arduino, middle pin to A0 of Arduino, and the left pin to ground of the Arduino.