Hi.
 
Are you using Arduino IDE or VS Code with PlatformIO?
 
When you get that kind of error, you must declare the functions before the loop() and setup(). That happens with some versions of Arduino IDE and with VS Code + PIO.
 
This means that you need to copy the initMicroSDCard() function to a place before the setup() and loop().
 
Let me know if you can get it working or if you need further help.
Regards,
Sara