Need help with sttrings!

HI everyone i have a string like
[LEFT][COLOR=#993300]var[/COLOR] stg:[COLOR=#993300]String[/COLOR] = [COLOR=#0000ff]"kuripa.org[/COLOR];
[/LEFT]

and an empty string
[LEFT][COLOR=#993300]var[/COLOR] stg_empty:[COLOR=#993300]String[/COLOR];
[/LEFT]

and i want to copy the third letter from string stg and paste to string stg_empty.

How can i do that can anyone help me plss ???