You shouldn't focus on any one exercise. Especially with legs. There's so many different ones. PP has great advice. Regularly rotate squats, lunges, step ups, stairclimber, deadlift if you can properly (use a hex bar if your gym has it. It's more leg focused). There are a ton of variations within these as well. Use dumbbells, one leg, etc.

Good way to gain any kind of mass is to lift heavy and eat properly. In general leg muscles are fast twitch muscles which responds to heavy lifting, you could do thousand squats without much gains except a "pump" which some people associate it as "toning." In your case, I would continue with squats and combine it with deadlifts. Squats are a quad dominate exercise and deadlifts are hamstring dominate, both key exercises to improve the posterior chain.

Perhaps I would try to limit deadlifts since it hits more thigh area. Lunges are great too along with step-ups (both quad dominate) and go heavy, you may want to utilize the "smith machine" for lunges. It's really all about which exercises you respond to eventually and everyone is different but i would stick to the core exercise mentioned to fulfill your goal and throw in accessory exercises or isolation exercises like hip bridges at the end. Or if you feel you need to diet down first and then build muscle. It's difficult to do both at the same time. Good luck!

Do lunges instead. Also pilates.

Is it a bad idea to focus in on squats? I see mixed comments online regarding making the legs look larger. I am a heavy pear shape in that no butt, but large thighs. Basically all thighs, my weight is carried heavily there and I am only 5'3 so my legs look very short and heavy as it is.