How to advance to do squats and deadlifts
You don't need a specific workout plan. You need to learn the basics of the movements. Without knowing the basics, you will remain "quite weak". There really isn't a magical workout plan for you. Your a beginner, which everyone was at some point, which means you need to start at the beginning. I have to applaud you on realizing that you need to be squatting and deadlifting. Many beginners are too afraid to learn the lifts and never get anywhere.
So here it goes.....
Squats take time to learn. The first thing you should focus on is mobility. Run an internet search for mobility exercises for squats and deadlifts. Focus on those for the next few months. These lifts take a decent amount of mobility in order to do safely and efficiently. Before you're ready for the barbell, work on prison squats with focus on proper form rather than how many or how fast you do them. As for deadlifts, you could use a broomstick and engrain the bar path into your mind until it become second nature. Again, this will take a lot of time and repetition.
Become a student
The squat and deadlift are essential for strength. They also are movements humans perform on a daily basis which is why many experts think they should be the pillar of any workout program. If possible, seek out coaching. Be cautious though, there are a lot of Bro lifters out there who have no business teaching anyone. Another, cheaper, option could be to use your phone and record your form. Many facebook sites will critique form for you. Just be prepared for blunt honesty because that's what you need. Youtube has more videos than you could possibly watch on how to progress with squats and deadlifts.
There is no reason to rush into these lifts. Rushing it will only cause injury which will cause you to remain "quite weak" and well as be in debilitating pain. Set short range goals that pertain to increasing mobility and learning to hit the "cue's" of the specific lifts as they are sometimes referred to.
While you are learning the lifts you should focus on push ups, bench press and other exercises that aren't as technical. Sprints are also a very overlooked exercise. They work wonders on your leg muscles and they're a good workout when you're short on time.