You mentioned that your primary concern is your weight (specifically belly and buttocks). Now, there is no such thing as targeted weight reduction, so in order to lose weight there you will have to burn it through a regimen of strength training, cardio, and dieting.
After nine years of relative inactivity, it is fair to say that just about any strength routine is going to give you great results thanks to the novice effect, which states that inactive individuals get in the first few months of training the largest strength gains and results than any other group. In other words, you will see great results simply by picking any routine and sticking to it.
That said, there are some routines that are far better than others and will give you better long-term results, especially with regard to your goals. Among those routines are the Starting Strength and Strong Lifts programs, both of which are very highly regarded. Bonus: doing squats is awesome for your butt.
For cardio, this is really up to you. As @BackInShapeBuddy said, Couch to 5k is a popular program for people new to running. If running isn't your thing (I personally hate it) you can swim, bike, hike, play sports, do pylometrics, tae-bo, jazzercise, chase squirrels in the park; really anything works, so be creative and have fun with it.
Finally, there is dieting. While the initial instinct might be to cut down on calories and overall food consumed, that isn't the right approach. You're going to be burning way more energy than you ever have in the last nine years, so eating a lot is important to keep your body fueled. What you need to do is cut out all of the "bad food." Specifically, you need to cut back (better yet, eliminate) empty carbs, highly processed foods, and sugary drinks from your diet. In other words, eat healthy, and make sure you are consuming enough protein to fuel your muscle growth from working out.