There is no conversion. It is starting over. If it was a Epicor CR to your version then that will be Epicor SSRS to your SSRS. We had about as many as you and converted the biggest ones and left the rest as CR. We are working thru them as we go. We did one BAQ report and as a simple report it was ok, but I am now moving to using an RDD like in the post below. Harder to start, but much more power and flexibility.
I made my users claim their reports and any that claimed them all, I waited for them to test and then did the ones they were “missing”. We had come from another system and a lot of them were trying to do things the old way.