Normally, there are a few places where you can check the OS version your computer is running.

One place you can check that is in System Information. (by launching msinfo32.exe)

You can also get that info from Winver (do a search of Winver and launch it)

Settings -> System -> About is another place that you can find this info.
If you need to find out the version of a remote machine, you can either RDP to that machine to get the information or ask the user to look it up for you. However, you can also do it with a remote PowerShell Session.
To look for the OS version, establish a remote PowerShell session.

Either CMD will get you the information you need.
[System.Environment]::OSVersion
[System.Environment]::OSVersion.Version
Below is a list of OS version taken from a Microsoft documentation.
Operating system | Version number | dwMajorVersion | dwMinorVersion | Other |
---|---|---|---|---|
Windows 10 | 10.0* | 10 | 0 | OSVERSIONINFOEX.wProductType == VER_NT_WORKSTATION |
Windows Server 2016 | 10.0* | 10 | 0 | OSVERSIONINFOEX.wProductType != VER_NT_WORKSTATION |
Windows 8.1 | 6.3* | 6 | 3 | OSVERSIONINFOEX.wProductType == VER_NT_WORKSTATION |
Windows Server 2012 R2 | 6.3* | 6 | 3 | OSVERSIONINFOEX.wProductType != VER_NT_WORKSTATION |
Windows 8 | 6.2 | 6 | 2 | OSVERSIONINFOEX.wProductType == VER_NT_WORKSTATION |
Windows Server 2012 | 6.2 | 6 | 2 | OSVERSIONINFOEX.wProductType != VER_NT_WORKSTATION |
Windows 7 | 6.1 | 6 | 1 | OSVERSIONINFOEX.wProductType == VER_NT_WORKSTATION |
Windows Server 2008 R2 | 6.1 | 6 | 1 | OSVERSIONINFOEX.wProductType != VER_NT_WORKSTATION |
Windows Server 2008 | 6.0 | 6 | 0 | OSVERSIONINFOEX.wProductType != VER_NT_WORKSTATION |
Windows Vista | 6.0 | 6 | 0 | OSVERSIONINFOEX.wProductType == VER_NT_WORKSTATION |
Windows Server 2003 R2 | 5.2 | 5 | 2 | GetSystemMetrics(SM_SERVERR2) != 0 |
Windows Home Server | 5.2 | 5 | 2 | OSVERSIONINFOEX.wSuiteMask & VER_SUITE_WH_SERVER |
Windows Server 2003 | 5.2 | 5 | 2 | GetSystemMetrics(SM_SERVERR2) == 0 |
Windows XP Professional x64 Edition | 5.2 | 5 | 2 | (OSVERSIONINFOEX.wProductType == VER_NT_WORKSTATION) && (SYSTEM_INFO.wProcessorArchitecture==PROCESSOR_ARCHITECTURE_AMD64) |
Windows XP | 5.1 | 5 | 1 | Not applicable |
Windows 2000 | 5.0 | 5 | 0 | Not applicable |
If you are running Windows 10, refer to below list for the build associate with the version.
