Hello Barbara,
Thanks for the question!
There are a couple of options from Ireland to France depending on where in Ireland you wish to leave from and where in France you wish to arrive!
There is a
Getting to Ireland page on our website, this is the usual page for our incoming travelers but can be used the other way. Select the Ferries option and enter the location of France, either Cherbourg or Roscoff will be listed and the ports here and the providers who offer the ferries. The providers are Irish Ferries and Brittany-Ferries, please follow the links to their websites for bookings. All of the crossings are long so the cabin option is available as standard.
Hopefully, this will help you sort out your plans!
Martin