Calculating TMB for TCGA data

Question

[Jaber]

Hi, community, I am facing a bit of a struggle to find the genomic region in Mb for the TMB calculations,

I am using the TCGA-READ data, where can I get the Mb value?

I want to calculate the TMB as follows = Total number of mutations / Mb.

I navigated Biostars' previous posts and couldn't find an answer to my question. Also, I looked up TCGA and didn't find any information regarding the Mb value (Megabase).

Is there any way I can infer the Mb from my data? Maf file of TCGA-READ I mean

I really appreciate any help you can provide.