Cardio or strength training

I am size 10 trousers and size 8 top. I am pear shaped. I want to get my trousers to size 8 as well but don't know if I should do cardio for my lower body or strength training. My calves are 12.5" and i feel they can still do with some cardio to get them down to 12" but haven't seen any difference in 4 weeks. What is the best way to basically drop a dress size?