Upgrading from Membership Pro to Membership 2 Pro

Hi,

I'm currently trying to update to Membership 2 Pro. I have Membership Pro installed on my site currently. Each time I click on the upgrade links I seem to be taken in circles. It seems I need to have version 3.5.3.3 of the Membership Pro plug in before I upgrade, but don't seem to be able to update. I'm running Wordpress 4.3.

Thanks