Where do i find this part of the definition?

[ann.staniford]

[Adam_M (Adam Mounsey)]

Its the Expression component, you can double click to edit the expression.

[mohamad.elatab]

or you can right click on u , expression, expression editor x+1 , so in this case you wont need this part!

[ryanhughes]

Or replace it with the addition component.
Pufferfish comes with a handy x+1 component - also attached.