Its not issue of C location. I used the below script its working now.
var bimdumperlocation="C:\\Users\\Sanket.Vaidya\\AppData\\Local\\imodelbridges\\ProStructures\\bimdumper.exe";
var input="--input=C:\\Users\\Sanket.Vaidya\\Downloads\\test.bim";
var dumpschema="--dump-schemas --dump-elements";
var signaturefile=Project.Variables.Var1 + " C:\\testabcd23.txt";
var command=bimdumperlocation+" "+input+" "+dumpschema+" "+signaturefile;
var cmd1=Sys.OleObject("WScript.Shell").Run("C:\\Windows\\system32\\cmd.exe /c" +command);