I recently went to Niagara Falls and I needed a program to convert MTS files. Most of the programs cost $40 plus, but then I found Handbrake.
Handbrake converts most any video formats to a handful of modern ones being MP4 and MKV. Handbrake converts videos for Mac as well as PCs.
It is an extremely easy program to use. Just follow the directions below while saving yourself $40.