Where can I find the software for a MacBook Air for the 9797 Lego Mindstorms Education NXT Base set?
You can download software for programming the LEGO Mindstorms NXT robots on macOS directly from the LEGO Mindstorms website.
The software is packaged in an ISO image, and there are instructions for how to install it also available on the same page.
Keep in mind that this is the retail version of the software, designed for use with the 8547 NXT 2.0 set, not the education version. The programming functionality for both sets will be the same, but the retail software does include some features specific for the 8547 set, such as building instructions, and does not include some features that the educational software does, such as data logging.