was giving my car a run when I went into 3rd gear it was like going into neutral . tried 4th gear and same thing car will not move, engine revs freely. However 1st gear,2nd Gear,5th gear and Reverse still works fine. turned off the car and selected 3rd then started the car and it did not roll forward.

WHat can be the cause of this?

 

Sounds like you broke the 3-4 shift fork.