If you can open the old code in notepad, then copy by highlighting/then right click ->copy, you can paste it into qbasic/quickbasic with the following.
(be sure the line lengths are not over 255 characters, and that
they end in CRLF. Also don't try to do it all at one time if it's more than a few
lines long; remove any control characters if necessary/possible ).
click in the qb program where you want the text.
right click on the Qbasic/QuickBasic in the tray. Go to Edit then paste
Another note: If you are trying to post entire SUBS/FUNCTIONS dont.
Make the sub or function in the normal way through the edit option of QB.
Then past from after SUB subname/FUNCTION functionname up to END SUB/END FUNCTION but not including it.