Sometimes the ssl format may be pfx. To convert to .pem you can use the following command (Note: often the file is password protected, as such you will need the password to change the file format):

openssl pkcs12 \ -in cert.pfx \ -out websitename.pem \ -nodes

You may then be prompted for the password
Please change cert.pfx to the name of the pfx file and change websitename.pem to the name you wish to call the formatted file.
Extracting information:
http://www.networkassassin.com/openssl-commonly-used-commands/