While you can download Windows Server 2012 R2 from official Microsoft sources (primarily for legacy archival or offline lab use), you should not use it for any system connected to the internet or handling real data. Its time has passed. Plan your migration to a supported version immediately.
Many tech websites and torrent platforms host ISOs. Do not use these. Files from unverified sources are frequently bundled with malware, rootkits, or altered components. There is no guarantee of file integrity. download windows server 2012 r2