Hi,
If built-in the theme SEO options are enabled, you can change it in Creativity -> TEmplate Options -> SEO tab.
If SEO is disabled, please check Dashboard -> General settings.
?cat=100 is the URL for the blog category, so only way to change it is by changing permalinks, name like #text-36 (contact) is from number of the widget with contact form (you can add i.e. another <div id="your_new_id"> at te beginning of this widget and </div> at the end, then you can change in Menu item URL #text-36 to #your_new_id