iZip Pro is a separate app and will not automatically import your files from iZip Free version.
In release 12.0, we made it easier to import your existing files from iZip Free to iZip Pro:
Please first make sure that you have both iZip Free and Pro versions upgraded to version 12.0. You can check the version on the Info screen.
In iZip Free, go to Settings. Tap Transfer Files to iZip Pro. All your existing files will be compressed into iZipFree.zip. You will then be prompted to select an App to open it. Tap "iZip Pro" then extract all files. All transferred files will be under the folder "iZipFree".