So you have a VMWare virtual machine and you want to migrate it to Qemu/KVM setup managed by libvirt? This is very easy, using libguestfs.
You will need libguestfs 1.37.10 or higher, which unfortunately is not available for Debian Stretch. The libguestfs-tools package in Debian Buster is fine though.
The command you need is this:
$ virt-v2v -i vmx /mnt/storage/vmware/vm/vm.vmx -o libvirt -of qcow2 -os storage-pool -n network
Replace storage-pool with the name of the libvirt storage pool where you want to store the new VM it, and network by the network name. In this example the disk images will be converted to qemu’s qcow2 format.
To get a list of all available storage pools, use this:
$ virsh pool-list
This command will show all available networks:
$ virsh net-list