No problem! Nowadays there’s plenty of choice when it comes to WCMs. We will get the full context that you have, and advice on suitable system. If you have already selected the system, we will advice on the content architecture, as well as automation of the migration process as much as possible, where it makes sense.
Sitefinity is extensible system, but you have to think for the future ensuring the right architecture of the newly moved data will help for scalability and easier maintenance later.