https://www.geotrust.eu/en/support/manuals/microsoft/all+windows+servers/export+private+key+or+certificate/

Next run OpenSSL to extract the private key, and the cert file

Export the private key file from the pfx file

openssl pkcs12 -in filename.pfx -nocerts -out key.pem

Export the certificate file from the pfx file

openssl pkcs12 -in filename.pfx -clcerts -nokeys -out cert.pem

Remove the passphrase from the private key

openssl rsa -in key.pem -out server.key