Lightroom needs to access the original image file you imported.
If that is on a 'Backup' drive, then that drive needs to be connected and available to Lightroom. Plug it in.
"Create a Saved Print" only saves the layout of the print design and a reference to the original image location. No image files actually exist in Lightroom.
i think my back up drive has the file. i imported the photo from my back up drive to library and then worked on the photo in develop module and created saved print before print.
You think it has the file? That's not really inspiring confidence. You need to VERIFY that you know the exact location of the file, and then make sure that Lightroom knows the location (you can do this by following these instructions: Adobe Lightroom - Find moved or missing files and folders )
The whole idea of using backups for actual work is not what I would recommend. And where is the original?
Go to the Library and use the menu command " Library/Find All Missing Files" and then find them with your OS and then relink them in Lightroom.