Great you’re thinking of upgrading 🙂
In a situation like this it’s worth emphasizing the importance of backing up before you begin and ensuring you know how to restore the backup – just in case something goes awry. If you can also do a dry-run in a duplicate testing environment, then better yet.
What I’d recommend in the first place is updating PRO and core to 2.0.11 – from there, try updating to our very latest releases. You can grab older versions of the PRO plugin here and older versions of the core plugin here.
One other thing, I noticed the pro version is called Events Calendar Pro and not The Events Calendar pro. Was there a name change at one point?
We may well have dropped the extra The or just become more consistent in our naming practices 🙂
Good luck!