Rolling back and resetting the branch

[BeefStu BeefStu]

I have a file called xx.c that was at version 3.5.5.0 and now it is at 
version 3.6.0.0 (no other check ins were done between those other versions).

can somebody please tell me how I can remove version 3.6.0.0 of my file and 
safely but me back to where I was.

I think I have to reset the branch, right.

Thanks in advance to all that respond