My name is Ashutosh Mishra
The problem you are facing can be caused due to LCD failure.
However, as your priority is to connect an external monitor and back up the data, you would need a VGA cable. The VGA port on your Inspiron1318 is on the left side of the chassis.
After connecting the cable to the Monitor, you need to press FN+F8 keys on the keyboard to transfer display to the monitor.
In this way you can see the display on the monitor if everything is fine with in the computer.
However, in case you are still not able to see any display on the monitor, then it might be a hardware failure.
To diagnose the same, Please follow these steps:
Turn off the computer.
Disconnect all the peripherals including the external monitor.
Hold the FN key and the power button simultaneously down for 5 sec to initiate the diagnostics.
The diagnostics will run and it will give error message on the screen or beep codes if the screen is faulty.
You can also refer to the following link for the steps as well: http://support.dell.com/support/topics/global.aspx/support/kcs/document?&docid=DSN_300428&isLegacy=true
Please reply back with the error code or the no. of beep codes that you get in the diagnostics.
Hope this helps resolve your issue.
Thanks and Regards,