Combine 3 Files into a .pfx programatically

I would like to combine 3 files into a .pfx file programmatically for an MQTT connection. I have tried several different combinations of suggestions, but I have not been able to get my desired result.

This is the terminal command that I would like to replicate:

 openssl pkcs12 -export -out final.pfx -inkey private.pem.key -in AmazonRootCA1.pem -in certificate.pem.crt

I have added more details of what I have attempted on this Stack Overflow question. Is this something that can be done in Unity?