Your FBK's are in NAD 83? Your dwg is assumed positions? Your post is a little lacking.
Import your survey data in your prefered manner and use coincident points to translate and rotate the linework from the drawing to the NAD 83 point data.
Basically i have topographic information in about three FBK files along with a dwg file. The FBK file is in NAD83 but not merged with base dwgs.
How can i merge them together?
I am interested in finding out the grade elevation..
is the base drawing in NAD 83? You can import the the FBK's using the Survey tab of the toolspace or by clicking "Import Survey Data" on the home ribbon. You probably want to read the help manual for survey data if you have never done this before.