The apex command expects a NUMBER not a bind variable. Change your statement to:
SQL> APEX EXPORT -applicationid 250
or perhaps use a host variable, &appid, for example:
SQL> def appid=250
SQL> APEX EXPORT -applicationid &appid
Thank you for your input and sorry for the very late reply, I thought I had already replied to you
No problem and thanks for marking the thread as answered, this may help others with a similar question/issue.