As Moonboots said, they are probably using Blender's built-in 'Voxel Remesher'. Alternatively you can use the Quad Remesher (either the built-in one, or a third party paid plugin with same name)
Remember however, before trying either, you should apply scale while being in
modelling viewport (not sculpt viewport). Without that, most of the time you will end up having non-ideal number of quads (too dense or too thin) & and in some cases even hang your PC for a while (End Task on Blender.exe in Windows Task Manager to get out of the hang)
The way to apply scale is in modelling viewport, select the object in object mode, and press
CTRL+A, and then select the
Scale option in the pop-up menu.
After that either remesh in Modelling viewport or while Sculpting, either is fine.
In modelling viewport, the method is Data icon (green reverse triangle) in lower right, then remesh menu. Remember to go with default value of 0.1 which give you less geometry and won't hang your blender first, before trying lower values.
Then hit the Voxel Remesh button.
In Sculpting mode, the method is to press
R first to decide visually the size of your quads. Move your mouse to reduce or increase the size. Once you are happy, Left Click to confirm. Don't worry, blender remembers what you chose. You can then safely do
In practice, people usually Remesh once before sculpting while in modelling viewport, then remesh again as needed during sculpting.