The "Tools" menu item is a default menu item and should be available in a correctly installed Sweet Home 3D.

The Cabinet Maker is a plugin that must be installed before you see it in the Tools menu.
First install the Plugins Manager which makes is much easier to install/remove other plugins. Using the plugins manager you can install the Cabinet Maker. Make sure to also install the Advanced Edit plugin, it's a must-have.

If you decide to use existing 3D models you can search for them on the internet. On my site dodecagon.nl I offer two kitchen cabinets libraries and a kitchen appliances library.