Конвертация PFX в CRT и KEY

openssl pkcs12 -in [file.pfx] -nocerts -out [file.key] -nodes
openssl pkcs12 -in [file.pfx] -clcerts -nokeys -out [certfile.crt] -nodes

CER -> PEM

open a terminal and run the following command

openssl x509 -inform pem -in certificate.cer -outform der -out certificate.pem