Backup VM flat.vmdk or vmdk?

Hi.

I have a VM on an ESX cluster 3.02. I want to 'migrate' this VM on a new cluster that is not reachable from the first.

So I want to copy my vmdk file to an other computer which  can access the two clusters. Then I will put the vmdk on a new datastore of the new cluster create a VM and chose 'use an existing VMDK' then start the VM.

The VM is stopped, now I want to copy the VMDK file but I have 2 vmdk files:

afmob-server.vmdk and afmob-server-flat.vmdk

What should I copy to then create a new VM with the vmdk? 2 files? Is my VM OK? is it normal to have 2 files?

Thanks

Alexaaaa