Help on preparing pem file for Google apps

I have installed my positive ssl on my plesk server but now I need to put it on google apps SSL. google needs two file:
1 . PEM encoded X.509 certificate
2. Unencrypted PEM encoded RSA private key

and I got from comodo four files:
Root CA Certificate - AddTrustExternalCARoot.crt
Intermediate CA Certificate - COMODORSAAddTrustCA.crt
Intermediate CA Certificate - COMODORSADomainValidationSecureServerCA.crt
Your PositiveSSL Certificate - www_domain_com.crt

I can create pem files but not sure which files to put on certificate or private key.

Can any body tell me what file (or if files which ones and in which order) to create the pem file for google’s each files.

Every time I try to add google says “Both the private key and SSL certificate should be in unencrypted PEM format”
I know I have put the correct .pem file as I can create pem files, I am assuming the content of the files and not how google wants it.

Many thanks for your help.

Which article of Google’s are you trying to follow because this may hold the key to how they want every thing?

Cant yet found any specific article to follow, however, by asking google support they replied:

[i]

I would like to inform you that before starting the SSL setup, please note that PageSpeed Service supports the following certificate types:
-Single Domain/Hostname
-Self-signed
-Wildcard
-Subject Alternative Name (SAN) / Multi Domain

It requires some things of your certificates and keys:

-Private keys and certificates should be uploaded in unencrypted PEM format.

-A certificate file can contain at most five certificates; this number includes chained and intermediate certificates.

-All subject names on the host certificate should match or be sub-domains of the domains that you’d like to serve through PageSpeed Service.

-Private keys must use RSA encryption. Maximum allowed key modulus: 2048 bits.[/i]

I used to have globansign SSL which had did worked, however, from comodo the name of certificate has changed a bit, I know there are the same/same purpose but I not skilled enough so far to understand which files to use and which order to use them. I have tried different ways and combinations but no luck so far… And the email reply google support sent me is bit beyond my skill to understand. If you understand any thing please guide me on how I can do this.

Many thanks