How do I copy VMDK files off Esxi file system?

Hello,

I have HDD with ESXi install which is not bootable, I'd like to copy just VMDK files off those HDDs to external HDD. What is the easiest way to do that? I envisioned something like booting system from USB drive and then copying files over that way but I have no idea what FS ESXi using and what USB boot image I shall be using.

Thanks,

G