How to generate a .pem
CA certificate and client certificate from a PFX file using OpenSSL.
You can use the OpenSSL Command line tool. The following commands should do the trick
openssl pkcs12 -in client_ssl.pfx -out client_ssl.pem -clcerts
openssl pkcs12 -in client_ssl.pfx -out root.pem -cacerts
If you want your file to be password protected etc, then there are additional options.
You can read the entire documentation here.