Pre-Migration Inventory Validation Report

It's been a very long time since I had to convert someone from 4.3.  I have a client that we just ran the pre-migration Inventory Validation Report for.  They have 24 pages of items that do not exist in IM1, but have data in IM2 and IM5.  They don't recognize the items.  I am assuming that during the conversion the system will ignore them since they aren't in IM1 but I just can't remember if that is true on not.

Does anyone else remember if they will just be ignored or if the conversion will stop???

Thanks

Sue