Can I use a certificate that was generated on a server?
Explaining better:
I have an environment like deiba my DNS server and my web servers on Windows and Linux.
I created a Wildcard certificate on my Windows WEB server (* .mycompany.net.br). And all applications on this server use a subdomain with this certificate. So far so good.
Now, I must use this certificate in an application that is on a Linux WEB server.
This applies to a subdomain (web2.mycompany.net.br).
Why am I going to need the .crt or pem file and the key. But I don’t know where to find it.
which Letsencrypt client did you used? Letsencrypt sends the certificate in the PEM format, so that client may have saved the certificate and converted it in a pfx or another format.
Then you can reuse the certificate.
But: You can create 5 identical certificates per week with the same set of domain names.
So it's possible you create a new certificate in your Linux environment. If you don't have a lot of errors, the rate limit shouldn't be a problem.