Open an elevated PowerShell prompt, make a note of your current directory, and run the following commands.

Get-ComputerInfo -Property WindowsBuildLabEx,WindowsEditionID | Out-File -FilePath .\computerinfo.txt
systeminfo.exe | Out-File -FilePath systeminfo.txt
ipconfig /all | Out-File -FilePath ipconfig.txt
Get-ComputerInfo requires PowerShell 5.1 or later. If your Windows Server version doesn't include Powershell, you can find this information in the registry. Open Registry Editor, go to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion key, and then copy and paste the Windows Server BuildLabEx and EditionID values.
Using File Explorer, navigate to the directory you noted down, and copy the files to a
USB flash drive or network location off of your computer.
After you've collected all of your Windows Server-related information, we recommend that you back up
your server operating system, apps, and VMs. You must also shut down, quick migrate, or
live migrate any VMs currently running on the server. You can't have any VMs running during the in-place upgrade.
Perform the upgrade
Now that you've completed your prerequisites and collected diagnostic information, you're ready to
perform the upgrade. In this section, you use Windows Server Setup to select the settings for
the upgrade. Windows Server Setup uses these settings to upgrade your version of Windows Server,
during which time your computer restarts several times.
To perform the in-place upgrade:
Using File Explorer, navigate to the Windows Server Setup media. Then open setup.exe.
For example, if you're using removal media the file path might be D:\setup.exe.
Important
Depending on your security settings, User Account Control may prompt you to allow setup to
make changes to your device. If you're happy to continue, select Yes.
By default, setup automatically downloads updates for the installation. If you're okay with
the default settings, select Next to continue.
If you don't want Setup to automatically download updates, select Change how Setup downloads updates, choose the option appropriate to your environment, and then select Next.
If prompted, enter your product key and then select Next.
Select the edition of Windows Server you want to install and then select Next.
Review the applicable notices and license terms. If you agree to the terms, select Accept.
Select Keep personal files and apps to choose to do an in-place upgrade, and then select Next.
After Setup finishes analyzing your device, it displays the Ready to install screen. To continue the upgrade, select Install.
The in-place upgrade starts, and you should see a progress bar. After the upgrade finishes, your server restarts.
Checking if your upgrade was successful
After the upgrade to Windows Server is done, you must make sure the upgrade was successful.
To make sure your upgrade was successful:
Open an elevated PowerShell prompt and run the following command to verify that the version and edition
matches the media and values you selected during setup.
Get-ComputerInfo -Property WindowsProductName
Make sure all of your applications are running and that your client connections to the
applications are successful.
If your computer isn't working as expected after the upgrade, you can
contact Microsoft Support for technical assistance.
Next steps
The following articles can help you prepare for and use your new Windows Server version:
Install or uninstall roles, role services, or features
Windows Server management overview
Get started with Windows Admin Center
Key Management Services (KMS) activation planning
Activate using Active Directory-based activation
If you'd like to learn more about deploying and post-installation configuration and activation options, check out the
Windows Server deployment, configuration, and administration learning path.