PHP Code:
<li><a href="/bakery/">Bakery<?php if((int)$_GET['cPath'] == 23) echo ' xxx-xxx-xxxx Ext. 1' ?></a></li>
(int)$_GET['cPath'] strips the category path down to its first numerical portion, which is the top category id. Replace 23 with the appropriate category id.
You find out the appropriate syntax for a given platform by studying its structure or by asking those who are familiar with it. It helps if you don't insult those who respond.
We couldn't tell you how to get the number into your output without a clue as to what the output is, as you gave with your subsequent posts.