Get the Hardware Hash
Log into the system.
Navigate to Access Work or School.
Click Export to export the management log files.
Navigate to C:\Users\Public\Documents\MDMDiagnostics and extract MDMDiagReport.zip.
Open the extracted folder and copy DeviceHash_{system name}.csv to a USB drive. (Don't modify the CSV Excel, it'll corrupt the format.)
Import the Hardware Hash into Autopilot
On your computer, log into Intune.
Navigate to Devices -> Windows -> Enrollment -> Devices.
At the top, click Import and on the left-hand side and select the location of the CSV.
It can take up to 15min for the device to show up in Autopilot.
Once it does, set the Group Tag.