Transfer of entire datasets from one app to another independent app is not practical or reliable. On the other hand, re-typing lots of old medical history is tedious and unnecessary in many instances.
So begin by exporting your pdf summary files from the old app. Usually you can just tap a share button and select Copy File option. Then paste summary documents directly into one of Tidy's folders, like Outside Data folder there for just this purpose.
Alternatively, you may prefer to archive the information by tapping Save to Files, and later download files when you tap Add + File button in Tidy app.
Of course, certain information may need to be entered into Tidy’s entry fields. When you do so, take a moment to review and tidy up what is essential. Use Tidy's many checklists, menus, and templates. Some find it helpful to type using an M1 MacBook - or iPad with external keyboard. Keep in mind that a lifetime of care need not be entered at one time - or maybe ever, if it's stored in files that remain accessible to those who may need to know.