Strength and aerobic endurance training force different adaptations in the body. To get stronger, you have to train for strength. Doing countless reps on bodyweight exercises, or any exercise for that matter, will produce little gains in hypertrophy(muscle mass).
Getting stronger is usually a misconception with those that have never tried it. They usually think that it has little health benefits, and has more to do with meatheads that have nothing better to do. Nothing could be farther from the truth.Training to get stronger will not only keep you healthier than standard cardio, but will also go a long way with injury prevention. Provided it is all done with proper form and in the proper intensity ranges. Muscle mass gained through a program deals with the quality of your nutrition (paleo vs. a diet high in processed carbohydrates like grains and rice) and the amount of calories you take in each day.
I could be wrong, but if switching from a primarily aerobic program, and do to your age, your body is probably low on its testosterone levels. Might want to ask Steve Low.
Also where do you work out? Local gym like golds or a crossfit facility?
Blair is right about the smith machine as well. In the beginning your strength program will be very basic, and will depend a lot on your recovery abilities ( sleep, nutrition, etc). A basic template would be 2-3 total body sessions a week. Mark Rippetoe's starting strength might be a good place to start. As well as finding a coach that can show you how to properly execute the lifts.
I know this is a lot to process for your question, hopefully some of the mods can provide additional insight.