Having trouble to eject portable device from windows?

When I trying to eject my mobile hard disk from windows, It often comes that

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Problem Ejecting USB Attached SCSI (UAS) Mass Storage Device
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This device is currently in use. Close any programs or windows that might be using the device, and then try again.
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OK   
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Here is a method to deal with this. It’s not to turn off the computer or to employ some commercial application. Searching the driver letter in Process Explorer, the application will list the processes that are using the driver. After killing these processes, it’s safe to eject the driver.

Where to download Process Explorer?
Process Explorer - Windows Sysinternals | Microsoft Docs
https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer

reference

How to Find Out Which Windows Process is Using a File | Gizmo’s Freeware
https://www.techsupportalert.com/content/how-find-out-which-windows-process-using-file.htm