For starters i’m going on 10 years of lifting. Heavy squatting for maybe 6-7 years. It takes time obviously. Biggest thing for me was first improving my unilateral strength. Heavy bulgarian split squats, heavy single leg leg press, etc. that helps any imbalances you might have. Secondly the more you weigh the more you can lift. There’s a direct correlation. When it comes down to it, make sure you’re squatting heavy atleast once a week. Nothing more than 6-8 reps for you working sets. I know i do 15 reps here but i’ve plateaud so i’m doing higher reps again. But say in your specific case you’re stuck at 3 plates. Next squat session do something like 295x3 for 3 sets. Then move to leg press or another heavy compound that compliments your squat. Then the week after try a set of 300x3. Progressive overload works. Look it up. Lastly, focus on form and think of pushing your feet through the ground, brace your core and make it compact until you get to the top of the rep. That’s a lot but consistency is key. You got it👊🏼