Converting presti to lut(cube). 8.5.1 Lightroom - not classic.

Converting presti to lut(cube). 8.5.1 Lightroom - not classic. How do I convert a preset to a cube in Lightroom? 8.5.1 Lightroom - not classic. I saw in a video that it exports as a cube, there's a button above the presets, but I don't have that. I have an AMD 8500 processor, so I can't install the latest versions. Maybe it's due to a version difference. I don't know.