Exporting Certificate/Signature from Mozilla Firefox

On the original PC, where the Client Certificate is currently installed on:

Launch Firefox web browser
Click the Tools menu, then select Options
Switch to Advanced tab
Click the View Certificates
Switch to Your Certificates tab
Select the Certificate you intend to export
Click the Backup button
Type a file name and choose a path that the certificate will be exported to and click Save
Enter and confirm a password which will be used for the encryption of the exported private key and certificate, and click OK
The export of the certificate is now complete
If you intend to use the certificate on a new computer, transport/move the exported (.pfx/.p12) file to a new PC/Laptop for later import