According to the manual, this monitor has an analog D-Sub connection and a digital DVI-d.
If you have any open USB-C ports on the back of the Mac, I would suggest a DVI to USB-C adapter. One such adapter on Amazon.
That it doesn't even have a DisplayPort option suggests this is very old monitor. A 2004 release date, actually. I would very much suggest rather than spending the money on a cable, I'd get a much newer monitor. There are plenty of 4K choices on Amazon that are right around $200. Then you not only have a much higher (sharper) resolution monitor, but options to use DisplayPort or USB-C.
The main drawback with the inexpensive models is they have cheap panels that only display the sRGB color range and gamut. Just about the smallest, least colorful RGB space in use.
Or, just get the cable to spend the least amount of money. Up to you.