Problem with MultiBit HD

My friend has a problem with MultiBit HD. He used to have a wallet with MultiBit Classic and he has all his backups on multiple USB keys. It's been a while since he used his Bitcoins and with the recent price increase he wanted to check out his wallet. He has a new laptop so he had to download the new version of MultiBit HD.

So, this didn't happened to me, I'm trying to write the situation as he wrote it to me.

When he opened the MultiBit HD they asked him to create a new wallet, so he did. Then from what he told me, they gave him a 12-word password and they asked him to get the file for this new wallet. He wanted to upload wallet so from what I understand when they ask him to get the file he took his old .wallet file. But the wallet opened and the balance is at 0$.

He basically created a new wallet, but he's still not able to retrieve his old wallet. This is exactly what he wrote me (in French, unfortunately, sorry).

"dans le fond quand j'ouvre MultiBit HD
ça dit Créer un nouveau Wallet
ou Récupérer un Wallet
Créer un nouveau wallet, ils te donnent 12 mots de sécurité qui devient le mot de passe de ton wallet
et ils te demandent d'aller chercher le fichier pour ce nouveau wallet la
donc j'ai fait ça, jsuis aller chercher mon fichier .Wallet
mais la ça ouvre avec 0$$$
Récupérer un Wallet ben les 12 mots c'est pour ouvrir le wallet comme ce que je viens de créer, mais ça ouvre encore a 0$"

It looks like MultiBit HD has changed the way to upload your existing wallets, what do you suggest he should do to have access to his wallet again? Like I said, he has multiple backup on different USB keys, he's just not able to upload it in the new MultiBit HD.

Sorry if this is not very clear, I will try to ask him more information.