HDMI to RCA adapter for newer macbooks.
otherwise you need your specific macbook model's monitor out port to RCA. Possibly to video only, then a phono to RCA adapter that you plug into the headphone jack of your laptop to get audio into the projector.
However, I think it is better to download the app "Boom" for Mac to enhance your MacBook's internal audio or just use some cheap computer speakers.
https://www.walmart.com/ip/Black-1-8M-6-Ft-Audio-Video-AV-Cable-to-RCA-for-PlayStation-1080P-HDTV-HDMI-Male-to-3-RCA-Audio-Video-AV-Cable-Cord-Adapter/558568795