how to read trace file format in ns-2

there is nothing special with file names (out.tr,win.tr etc.).

But to learn about trace analysis, you may start with the following links

http://nsnam.isi.edu/nsnam/index.php/NS-2_Trace_Formats
http://bunlab.twbbs.org/ns2_trace_format.htm
http://www.winlab.rutgers.edu/~zhibinwu/html/ns_trace.html
http://mailman.isi.edu/pipermail/ns-users/2003-October/036546.html (but now, it seems that tracegraph is not available for download)

Further, there are so many awk, perl and other scripts freely available for trace analysis.