Archiving email for backup is important. However you will need to know the location of your archived file before you are able to re-open/restore it.
Follow the steps below to find the location of your PST file.
  1. Open Outlook
  2. Select the mailbox you need to find the location
  3. Right-Click selected mailbox and click Open File Location

  4. A windows explorer popup will appear showing you the location of selected mailbox file, as shown in image below. (You may select and copy the location)