https://support.ssl.com/Knowledgebase/Article/View/19/0/der-vs-crt-vs-cer-vs-pem-certificates-and-how-to-convert-them

openssl x509 -in rootCA_hrm-ftp.cadena-it.com.pem -outform der -out rootCA_hrm-ftp.cadena-it.com.der
openssl x509 -in rootCA_hrm-ftp.cadena-it.com.pem -inform pem -out rootCA_hrm-ftp.cadena-it.com.crt