For a basic, initial analysis of the contents of a carrier or transfer, we use PowerShell:

gci -file -recurse -force | group extension | select name,count,@{n='Size(GB)';e={ ((($_.group | measure length -sum).sum)/1gb).ToString('N2')}} 

This gives the number of total file size (in GB) of all files in and under the present working directory, sorted by extension.