Sizing an Aurora Instance vis a vis DynamoDB

Question

I'm trying to size the proper Aurora instance type for a conversion from DynamoDB. How would I convert Dynamo's current peak reads/sec and writes/sec to an appropriate Aurora r5 instance type? The IOPS metric seems to be just traffic between Aurora and its backend data store, whereas front-end reads and writes will be largely serviced from cache.

And before anyone screams too loudly, I know there are vast differences between the models of a KVS like Dynamo and an RDS, and no accurate comparison is possible with just those 2 numbers. Just looking on guidance on how I might proceed with obtaining a reasonable estimate.