>>
>>Also, keep in mind that when you're performing a backup on the server, the server can only access itself and not the user's computer.
>
>Dear Teacher Naomi
>
>I am unable to understand what you said in above sentence.
>Please write again in some easy wording.

The disks in your command ("c:\" etc) are disks on the machine where SQL server service is running, not on the machine where you sit. So the path of your backup needs to be on the server, and needs to exist on the server - or, if it's a network path, it has to be visible from the server. Because that is where the commands you send will be executed.