Data Migration User stories
We're now working on moving data from our old system to a new and improved one in a project called data migration. This includes shifting features like account balance and instant fund transfer, as well as moving all the information about our customers, including closed accounts. Since I'm the product owner, I have to write user stories for this, but I've never done this for a data migration project before. Can someone help me figure out where to begin?
Help the Developers to understand the quality required, and where they will need to experiment and innovate while committing to that standard.
I agree with @Ian. But I'm also going to state that this sounds very much like a large technical debt initiative. In cases like this, I encourage the one fulfilling the Product Owner role to follow the advice of the Scrum Guide.
The Product Owner may do the above work or may delegate the responsibility to others. Regardless, the Product Owner remains accountable.
But who would know best how to accomplish the goal that your team is undertaking so that you could delegate the responsibility? Maybe some individuals that are responsible for knowing the technical details? Maybe some individuals that use that kind of information on a daily basis?
Ask your Developers to help you capture the information that is needed to do the work in a manner that will enable them to do the work in the fastest, most valuable manner.