There are many things to consider when migrating to SP online. Things most important to ask are what functionality to you currently have and can the cloud support it. Not everything in an on-premises installation can be done online.
You need to do a complete analysis as suggested here:
There is no support for content migration, so everything has to be done manually or through a third party migration tool.
There is no support for server code only apps using the new App model. So if you have any custom c# / server side code, you have to migrate that manually.
The better question to ask your boss would be why does he think it is beneficial to move to the cloud? Is it to save on infrastructure costs? Is he ok with having Microsoft handle all your data? Hybrid solutions are perfectly acceptable and depending on the complexity of your setup, may be a wiser choice: