if you just upgrade an existing APEX instance, your applications, IR and saved interactive reports will automatically be copied over into the APEX 4.2 schema/repository.
If you setup a new 4.2 system and go the export/import route, you should in addition to Jitendra's instruction also set "Export Interactive Report Subscriptions" to Yes.
I would personally just upgrade if possible, that's a lot easier. You can always step back to 3.2 as outlined in the installation notes (or restore a backup).
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