Where are calendar files stored?

In what folder or file are the personal entries to the calendar. I uninstalled eMclient and the new version has lost my previous entries

There is not one file that has local events. All data is stored in a database and you need the complete database to view it.

Uninstalling eM Client will not delete local data unless you choose to delete the database folder during the uninstall, when asked. If that is what happened, the only chance of getting back the lost data is to restore your most recent backup.

All other data synced with the server, will be available again after adding the accounts.