Keypad command line programming

I want to do a project were I have a numerical keypad connected to an arduino with a 16x2 LCD and I want to control 6 or more LEDs and there brightness. What I would like the key pad to do is if I want led 3 at 50% I would type in {3@50 enter} and the led goes to 50%. I am not sure how to do a command line type of thing in arduino

That sounds relatively easy, but it depends on your level of expertise.

Read the keypad output until the 'end of input' indicator (return) is received.
As each character is read add it to an array of characters before reading the next one.
When the input is complete, parse the array to determine the LED to be set and the required level.
Set the LED to the required level and go back to reading input.

Use an array of chars to hold the input not a String.

How much of the above do you understand ?
Have you successfully read single characters from the keypad and displayed them in the Serial monitor ?

is there any examples?

is there any examples?

Yes. Have YOU looked?