Hi Bibi,
Google's Keyword Tool has been turned into Keyword Planner. You can still use it for free, but you need to login into Google Adwords account first. The new tool is slightly different. Here is a good
article about that.
You can also try
Bing Keyword tool. Its free, but you also have to setup an account with them. You can probably find other free tools if you replacement for them online. Let us know if you find better alternatives. Thanks!