Here are the steps on how to open Google Takeout files:

1. Download the Google Takeout archive file to your computer.
2. Unzip the archive file.
3. Depending on the type of data you downloaded, you can open the files using a variety of applications, such as:
   • Gmail: Import the MBOX file into an email client like Thunderbird or Outlook.
   • Calendar: Import the ICS file into an calendar client like Apple Calendar or Google Calendar.
   • Drive: Open the ZIP file in a file explorer or unzip it and open the individual files.

If you are unable to open the Google Takeout files using the above methods, you can use a third-party Google Takeout file viewer or converter.

Read more: https://www.shoviv.com/blog/how-to-open-google-takeout-files-and-view-emails/