Migrate from private Gitlab CE instance to gitlab.com

My company is running a private gitlab CE instance.

Since we are a small team with less than 20 users, I’m thinking if it wouldn’t be safer to host our projects on gitlab.com since private repository are free and unlimited.

I would like to know if there is some difference between gitlab CE and free private gitlab.com repository.

If there is no difference, I would like to evaluate the cost in time to migrate all the repository, users, issues and wiki.

Is there some tool to move easily to gitlab.com?