In case if the requirement is to get new and repeat visitors comparison from one period to another period, then within the workspace, the same can be broken down with a time dimension of a selected time period.
If that's not what the requirement is, then is there a way where you will be able to identify a user (ex: Visitor ID or Experience Cloud ID).
In case if you have any such identifier (variable/eVar or prop), then you can create a custom segment and apply it to the user retention report for both previous and current time periods and you may get what you are looking for.
If none of this works, kindly share more details on what are you trying to achieve so that we can help accordingly.