If the web server is Apache (aka httpd) then the certificate and key files are specified in a .conf file, the same way as Apache on Linux, for example:
SSLCertificateFile /path/to/my.crt
SSLCertificateKeyFile /path/to/my.key
SSLCACertificateFile /path/to/bundle.pem # Optional
These entries may be in a <VirtualHost> section specific to the site, especially if the server is hosting multiple sites.
So you need to find where the server's Apache installation keeps its .conf files (c:\httpd\conf?) and find the file containing the current SSLCertificateFile and SSLCertificateKeyFile directives pointing to the presumably expired certificate and key files. Once these have been changed to use the new certificate and key files then you need to restart the Apache service to re-read the .conf file. Hopefully Apache or httpd is listed in the usual Microsoft Windows Services console.
As Richard says, this is a purely server admin issue, Moodle doesn't know about these certificates.