Upgrading payroll from Standard to Advanced - what info to save?

I have to upgrade my payroll as I now need to do payrolling of benefits and can't do this in standard.  As I have discovered, I will lose ALL my payroll data at the point the switch is done.

My question is (apart from why is this even the case?!) is what reports should I download to have the correct figures to transfer over, and also to keep with the records for data compliance?

I am planning to do this at the start of the next tax year to hopefully make it less painful.