I use following link. It is more recent.
In my opinion the "qemu-img" method is the easiest one.
https://www.nakivo.com/blog/how-to-convert-vhd-to-vmdk-a-step-by-step-guide/
Using qemu-img in Windows
Download qemu-img from the official web site (32-bit and 64-bit installers are available to download). In the current example, qemu-img-win-x64-2_3_0 is used. Extract files form the downloaded archive, for example, to C:\Programs\qemu-img. Then launch the Windows command line (CMD) - Press Windows+R to open the “Run” box. Type “cmd” into the box and press Ctrl+Shift+Enter to run the command as an administrator.
Go to the qemu-img directory:
cd C:\Programs\qemu-img
Commands of qemu-img in Linux and Windows are identical.
Convert VHD to VMDK in Windows
Run CMD as administrator and go to the directory where qemu-img is installed.
View the virtual disk information:
qemu-img.exe info c:\Virtual\Hyper-V\test-disk.vhd
Convert the VHD disk image to the VMDK format:
qemu-img.exe convert -p c:\Virtual\Hyper-V\test-disk.vhd -O vmdk c:\Virtual\Hyper-V\test-disk.vmdk
Where:
-p – show progress
-O – the output file
Wait until the conversion process is finished.