How do I wire a switch to a fixture that is served by wires in an iron pipe?
Do not cut the pipe. It may not be electric but water or gas (it looks like it may be black which is standard for gas).

A much simple approach is to drop a new line from the box behind the current sconce. This box obviously has one always on circuit. You can tap into this to run another circuit down the wall to a new outlet.  You also can add a pair of wires between the hot lead to the current light and a switch mid wall.

This requires using wiring that meets both local code and any restrictions your building may impose. In many jurisdictions this is non-metalic cable, but check.

If there are no hollows in the concrete (there would be if it were concrete block rather than solid concrete), you will need to cut a channel in the concrete to do this.  

An alternative is to use surface mounted metal raceways and boxes, such as these.





Your inquiry suggests that you have very little experience with this type of project. Working alongside someone with more experience is highly desirable whn learing to work with electricty. I would urge an experienced helper, or turn to a pro.