On Linux right now but here's what I think you'll need to do. Part 1: save the result of your FIND
command to a variable, and 2: take a substring of the variable. The second part is simple, so I'll start with that (assuming that in the first step you named your variable var
@echo %var:~-2%
That's about as far as I'm comfortable in batch, so this next bit is cobbled together:
To store the result of your find as a variable, try amending your code to:
set cmd="WMIC LogicalDisk Where VolumeName='MY_USB' Get /Format:list | FIND "Caption=" "
FOR /F %%i IN (' %cmd% ') DO SET var=%%i
and then (remember above) output it with:
@echo %var:~-2%
The related question from which I am cobbling together the second part is this question so if this doesn't work as expected I would jump over to that one first.