How to calculate TMB for somatic data TCGA

Hi,
I have to calculate for the first time the tumor mutational burden (TMB) for each sample of a big maf file of TCGA (gdc.cancer.gov/about-data/publications/mc3-2017) (the maf file), I'm a beginner on bioinformatic and coding and I didn't find any tool that allows me to calculate TMB for each sample. Does anyone know a tool for TMB calculation or can told me how can i do it for each sample?

Thank u and 'm sorry if my question is a silly question...