Since the older version(s) of mSecure isn't a cloud-based app, there is no way to "sign in" to an account where your information is stored online. Because of this, each older version of the mSecure's login password is device specific and your information is not automatically restored when an older version of mSecure is installed or reinstalled on a mobile device.
If you previously set up iCloud or Dropbox syncing in mSecure 4, you can set up the feature again in mSecure 4 on your device to sync in your information.
If not, if you made any mSecure backups through either the Email Backup feature found in the preferences or through using our free backup software called mBackup, you can use our mSecure 4 iOS guide to learn how to restore from a backup file.
We have an automated reminder in the older iOS app for making backups, so it is possible that you made an email backup some time in the past. Please search in your email accounts to see if you can find an email with "mSecure", "mism" or "mscx" in them. If you find an email backup you can use this guide to restore from an email backup file: https://support.msecure.com/knowledge-base/ios-email-backup