What to consider

If you have properly mapped your organization’s data, you should have a good idea of the number of documents you expect to migrate. The easiest way to estimate how long this will take is to carry out trial runs and time them.
A. Time Estimate
After testing, you should have a good idea of how long it would take to carry out the migration of a single document, which could look something like this:
B. Resources

Evaluate what will be required in terms of additional hardware, software, temporary disk space, external consultants, and internal resources.

C. Potential Risks

Understand potential risks and identify the roles and responsibilities of all parties involved in the project.