Warning: There is a high probability of this causing your service to stop working. Using the built-in Save / Restore option in game panel is preferable.
HOW TO RESTORE FROM AN AUTOMATIC BACKUP
Space Engineers will automatically save backups for you as you're playing. Restoring from the backups is as simple as moving some files.
Before we begin, make sure that your server is turned off before making any changes to files!
Firstly you will want to find the folder that your game is saved in. You will use the file manager in Game Panel for this. Select your game service, and open the File Manager. Find the "WORLD" folder and open it, then the "Saves" folder.
(This should be in Instance\Saves\<your world name> )
Here you should find all of your saved world files. Select the folder of the save that you want to restore, then open the "Backup" folder inside it. You should see the five latest backups of your server, with their date and times listed. Open the folder of the backup that you want to restore.
Transferring Backup Files
Once inside your backup folder, select all the files inside and click the "Create Zip" button at the top. This will create a .zip file within the folder. Use the globe icon beside the new .zip file to download it to your computer.
With your newly downloaded file in hand, make your way back to your world folder (the one named after your world). You should see the "Backup" folder at the top, with some other files below it. Select all of these files (not your "Backup" folder!) and create a zip file backup of these, then you can delete them.
Click the Upload button, and upload the .zip file that we downloaded. Once it has been uploaded, click the Extract button to the right of the globe icon. This will extract all the contents of that file into your folder. With all the new files in place, select the .zip file and delete it.
Once you've completed the steps above, you will have deleted your current save and replaced them with the backed up save. Exit the File Manager and click the "Start" button to turn your server back online.