Execute the following commands to convert an .crt file to a .pem file:
openssl x509 -in input.crt -out input.der -outform DER
openssl x509 -in input.der -inform DER -out output.pem -outform PEM
openssl x509 -in input.der -inform DER -out output.pem -outform PEM
The file output.pem is now PEM encoded.