How do I search by file extension in MacOS Finder?

In trying to search for a .ai file, I have tried doing kind:ai, and have also tried doing it via the kind selector (see image below). I know how to do this using the linux "find" command already, but I really want to find a way to do this using the native finder interface.

Solution 1:

OK, I finally figured it out with the following approach:

1. Open finder to the top-level directory you wish to search
2. Press ⌘ + F
3. From the search menu options, on the left, choose other
4. Click the checkbox under the In Menu column for file extension from the popup window and close the popup window by pressing OK
5. Select file extension from the search menu
6. Type your file extension in the text field (follows the word is)