27" iMac display used with M1 iMac

[BillB]

I hva a 27" iMac (Late 2009, 2.66Ghz nel i5) running 10.13.6, I would like to use as an additional monitor for a recently purchased M1 iMac running Ventura 13.2.1. Ideally, I would also like to use the older iMac as a repository for older files. It has a 20 GB SSD. What would I need to know or purchase to achieve this?
Thanks for whatever help you can provide.

 

[MacsBug]

I do this using a Luna Display (https://astropad.com/product/lunadisplay/)

On your 2009 iMac, you need to run the Luna Secondary app and set it to launch at startup.

On the new iMac, after installing the Luna Display app, you would plug the Luna Display dongle and enjoy a 2nd display.