If we have 2D surveying points inserted to AutoCAD and each point has its elevation written beside, can we convert all these points to a 3D points by one command in AutoCAD? If yes, what's the command name?

inserting these points from the begining in2D is not of help to convert to3D if you just have a simple text with their elevation written beside it.

next time insert the surveying points in3D with their respective elevations drawn, and then you can work from there by viewing their top view or side view or whatever view you want to see.

good luck.

i think there no one step in these case , you can repossession point with its Z value and convert to contor with small program you can download from net .   

There is no command to do that in AutoCAD but in AutoCAD Civil3D you can do that by a command name "MOVETEXTTOELEVATION" so all texts will be moved to its values in Z direction so, each text's insertion point will be in3D