Converting ISO disk images to DMG format should be easy enough nowadays and can be done in most, if not all modern disk image handling utilities, but it is unlikely you will find a dedicated iso to dmg converter only.
In most cases iso to dmg conversion is achieved because for Mac users .dmg files might be easier to handle compared to .iso files, but most recent disk management utilities for Mac have no trouble with either of these formats.
However, keep in mind that this won't work if you are trying to convert some Windows program installation disks to Mac one, that is simply not possible.
Updated: June 13, 2023