How to build strength for middle-aged adults

I usually manage my blood sugar levels. It feels like it's been several years since I started paying attention to my blood sugar, and as a result, I have learned many new facts. Recently, I read that muscle strength helps with blood sugar control. In particular, thigh muscle strength is said to be very important. However, because of my age, I am afraid of injuring myself while doing exercises to improve leg strength, so I haven't tried anything. I am curious about what kind of exercises would be helpful for improving leg and thigh muscle strength for middle-aged and older adults.