To copy a virtual machine from one computer to another

Create an empty virtual machine with the name of the cirtual machine you want to migrate.
You need to copy the following directories to the destination computer at the local username directory there.
C:\Users\Morteza\VirtualBox VMs
Change the machine UUID

The bridge connection might not be properly set, just open the settings of the virtual machine and you can choose the proper network adapter device off of the available options on the new PC.