In JMP 16 you can use Transform Each() like this
L = {10, 200, 3000};
L = Transform Each( {v}, L, Char( v ) );
Show( L );
By default the output container matches the input container. You can use output(...) to control it:
L = [10, 200, 3000]; // actually, an array or matrix, not a list
L = Transform Each( {v}, L, output( "list" ), Char( v ) );
Show( L ); // L = {"10", "200", "3000"};
For huge lists and matrices, this will perform a little better than the plain for loop.
Craige