This will help to extract pem private key from PFX certificate.
If you want to extract private key from a pfx file and write it to PEM file
openssl.exe pkcs12 -in publicAndprivate.pfx -nocerts -out privateKey.pem
If you want to extract the certificate file (the signed public key) from the pfx file
openssl.exe pkcs12 -in publicAndprivate.pfx -clcerts -nokeys -out publicCert.pem
To remove the password from the private key file.
openssl.exe rsa -in privateKey.pem -out private.pem
This is required as, at the time of exporting privateKey, you have added a password to the private key to secure it. If you left the password with it, it will keep asking the password as any application tries to access it.