Hello AndrewNguyenTruong,
Thank you for using Apple Support Communities.
We understand that you are not able to select the internal microphones as a sound source on your MacBook Pro as they are not available for selection in the Sound preferences. We would first recommend resetting the NVRAM and SMC on your MacBook Pro.
Reset NVRAM or PRAM on your Mac - Apple Support
How to reset the SMC of your Mac - Apple Support
If you continue to have the same issue, restart the computer into safe mode and try again.
Start up your Mac in safe mode - Apple Support
Let us know how it goes.
Best regards.