Switching from sub directory to sub domain

I have a multisite which is set up in sub directory mode, it was set up by a previous developer and I can see 4 sites set up. These sites have been set up as entirely new domains with the domain mapper tool. I need to know if it is possible to switch from this development set up to a production set up with completely new domains.

Currently when I try to add a new site to a new domain I get this error -

'Missing or invalid site address.'

Thanks for any help, hugely appreciated.