ssl certificate (server.cert)

[Crosznet]

Hi I had ssl before and my certificate ran out I tried to renew it but the company`s on the web wont send a server.crt now just 3 files wish go in the config. I have done all that but server.crt takes over now down to the questions.

1. Where can i get an online server.crt from a company to make my ssl work?
2. Am i doing something wrong?
3. What should I be Doing?

Thank you in advance.