Activity carrying over from Lead to Account after Qualifying

Hi,

Here is my scenario:  I need to know how many Orders are on Accounts, that had Appointment activity on them.

However, many appointments were set up on the Lead.  When the person buys, the Lead gets converted to an Account/Contact.  Therefore, when I do an advanced find for completed Appointments regarding Accounts that have Orders on them, it leaves out all the Accounts that had the Appointment regarding the Lead instead of the Account.

So, is there a way to search for all completed Appointments regarding Accounts OR Leads? 

Thank you very much in advance, everyone has been so helpful on this forum.