Import or convert Virtualbox image to Proxmox

I'm new to Proxmox and try to find a way to import or convert a Virtualbox image to Proxmox.
My Virtualbox image contains three files; .mf, .ovf and a .vmdk file.
So far i can't find a howto or tutorial. :confused:

Is there someone who can point me in the right direction.

Thanks in advance.