The command in your screenshot is wpeinit, which is a Windows PE (WinPE) command, not a normal Windows Server command. If Server 2025 has been booted into WinPE/command-prompt mode, the equivalent is:
X:\Windows\System32\wpeinit.exe -unattend:"C:\Unattended-PE.xml"
You can first verify that the executable exists:
dir X:\Windows\System32\wpeinit.exe
If it exists but wpeinit by itself says "not recognized", use the full path shown above. Also make sure the XML is actually on the drive you reference. For example, if the file is on the installation USB mounted as D:, use:
X:\Windows\System32\wpeinit.exe -unattend:"D:\Unattended-PE.xml"
Server 2025 Server Core's normal command prompt is not WinPE. If you are at a Server Core C:\Windows\System32> prompt after Windows Server has booted, wpeinit is not expected to exist, and there is no Server Core equivalent of wpeinit -unattend. In that situation, if your objective is to apply an unattended answer file during Windows Setup, you would normally launch Setup with the answer file instead:
setup.exe /unattend:"D:\Unattended-PE.xml"
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hth
Marcin