I don't think you can retrieve it as it will be encoded.
You can log in to the router and change it to one you can remember (or write down).
Access is via a browser to (http://) 192.168.0.1
You may need a username and password if you didn't set it to log you in automatically.
The default is usually written on the bottom of the device, I believe it is admin/password - but if you changed it then enter whatever you changed it to.
If you have forgotten that as wll then reset it to the default:
1. Press and hold the Default Reset button on the back until the Test LED turns on (10 secs).
2. Release the Default Reset button and wait for the router to reboot.
As it is a wireless router you will want to use encryption.
If in doubt, search online for the manual and download it.
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