How can i create an PKCS#10 file on a windows server 2008

As Mahesh shared most of the relevance. I just to add a use case for CSR like "Request a certificate for an IIS web", you can check out these steps which I did see relevant though article is old and not it is more of in house Microsoft CA. But it should applicable with e CSR given to third party CA
http://www.windowsnetworking.com/kbase/WindowsTips/Windows2000/AdminTips/IIS/RequestacertificateforanIISwebserver.html 

There are also case of using openssl too from https://www.openssl.org/docs/apps/req.html#examples
e.g. Generate a self signed root certificate: openssl req -x509 -newkey rsa:1024 -keyout key.pem -out req.pem

One useful online tool to check CSR formatting is handy as well to verify that it contains the correct information
https://www.sslshopper.com/csr-decoder.html

there is even CSR generator online
e.g. OpenSSL CSR Wizard   - https://www.digicert.com/easy-csr/openssl.htm
e.g. CSR generator - https://csrgenerator.com/
e.g. another using openssl (as well) https://www.openprovider.co.uk/ssl-certificates/csr-generation-tool/
e.g. Has generator, decoder and ssl checker- https://www.gogetssl.com/online-csr-generator/