Change all adapters of a vm named ‘myvm’ to while keeping all other settings like mac address:

• E1000:

  get-vm 'myvm' | get-networkadapter | set-networkadapter -type e1000

• vmxnet3:

  get-vm 'myvm' | get-networkadapter | set-networkadapter -type vmxnet3

• all possible values:

  e1000; Flexible; Vmxnet; EnhancedVmxnet; Vmxnet3