This article will show you how to convert pem file to crt and key file.
Convert pem file to crt file with openssl
openssl x509 -in /etc/letsencrypt/archive/domain/cert5.pem -out domain.crt
Convert pem file to key file with openssl
openssl rsa -in /etc/letsencrypt/archive/domain/privkey5.pem -out domain.key