The smith machine is a good tool to use for squats. It is great for building strength and increasing the max weight you can lift.
But…
You should be aware of the limitations of doing a squat in a smith machine.
The smith machine, since it follows a guided path, does not allow the same feedback you get from doing a free barbell squat. A smith machine does the stabilizing work for you, which makes it safer, but will not help you correct bad form or strengthen important stabilizing muscles.