Yes, it`s possible on a Destination
step of the wizard.
You need to:
1)Click the "Pick datastore" for selected virtual disks link.
2)In the "Choose VM Files Location" window, click "Add VM" on the right and select VMs whose disk format you want to change.
3)Select the added VM and click "Disk type" at the bottom of the window.
4)In the "Disk Type Settings" section, choose the format that will be used to restore replica disk files: same as the source disk, thin or thick.