Question

where should the object be placed in front of the concave mirror so a s to obtain its magnified,erect image???

Answer 1

Between pole and focus of concave mirror.

Answer 2

A magnified and erect image is always virtual. you can't capture it on a screen. 
It is possible in case of concave mirror only when the object is placed between pole and focus. The image id formed behind the mirror and it is virtual, erect and magnified.