Converting to bibitem in LaTeX

I agree whith the general process explained in the comments, but i think that they don't fully address the final task that you must do you for the conference, which very likely want a single self contained .tex file.

Let's assume that you have mypaper.tex which is your text with some \cite{<key>} and a refs.bib file. Then :

1. Firstly, put in mypaper.tex the two lines :

   \bibliography{refs} \bibliographystyle{plain}

2. Secondly run (instead of using the \nocite which has two drawbacks: (1) ordering as in refs.bib and (2) cites refs. that are not \cite-d in your paper) :

   (pdf)latex mypaper bibtex mypaper

   If this step is successful you will get mypaper.bbl containing the bibitem-s and a mypaper.blg which is BiBTeX's log file. (Nota : latex reads the mypaper.tex -- and when present the mypaper.bbl file -- but bibtex reads the mypaper.aux created by latex).

3. Thirdly, (optional but recommended) make sure that all the reference are correctly inserted and displayed in the file with :

   (pdf)latex mypaper

4. Fourthly, open mypaper.tex, comment out or discard the two \biblio... lines and paste the whole content of mypaper.bbl at the place where you want to get the bibliography. You then have the final self-contained file.

   You can run (pdf)latex mypaper at least two times to get the final .dvi or .pdf.

Edit: This copy-paste holds if he .bbl file content start with the regular \begin{thebibliography}. If it starts by loading packages with \usepackage{<name>} or even by \input{<name>.sty} (where <name>= csquote, url, etc.) you must move them in your preamble. If it starts by defining commands, your can keep them at this place or move them to the preamble.

Note for the OP: you use plain as the format, which looks strange for me. Actually each conference/organization generally has its own .bst style file which produces \bibitem formated accordingly to their editorial rules. More specifically, make sure that you need an alphabetical-ordered or a citation-ordered bibliography. In the later case, you must use the unsrt.bst (or a variant) in place of plain.bst.

The Python code to convert refs.bib file to bibitem file

python2 bibtex2item.py < refs.bib > bibitem.txt

# filename: bibtex2item.py
import sys

bibtex = sys.stdin.read()
r = bibtex.split('\n')
i = 0
while i < len(r):
  line = r[i].strip()
  if not line: i += 1
  if '@' == line[0]:
    code = line.split('{')[-1][:-1]
    title = venue = volume = number = pages = year = publisher = authors = None
    output_authors = []
    i += 1
    while i < len(r) and '@' not in r[i]:
      line = r[i].strip()
      #print(line)
      if line.startswith("title"):
        title = line.split('{')[-1][:-2]
      elif line.startswith("journal"):
        venue = line.split('{')[-1][:-2]
      elif line.startswith("volume"):
        volume = line.split('{')[-1][:-2]
      elif line.startswith("number"):
        number = line.split('{')[-1][:-2]
      elif line.startswith("pages"):
        pages = line.split('{')[-1][:-2]
      elif line.startswith("year"):
        year = line.split('{')[-1][:-2]
      elif line.startswith("publisher"):
        publisher = line.split('{')[-1][:-2]
      elif line.startswith("author"):
        authors = line[line.find("{")+1:line.rfind("}")]
        for LastFirst in authors.split('and'):
          lf = LastFirst.replace(' ', '').split(',')
          if len(lf) != 2: continue
          last, first = lf[0], lf[1]
          output_authors.append("{}, {}.".format(last.capitalize(), first.capitalize()[0]))
      i += 1

    print "\\bibitem{%s}" % code
    if len(output_authors) == 1:
      print output_authors[0] + " {}. ".format(title),
    else:
      print ", ".join(_ for _ in output_authors[:-1]) + " & " + output_authors[-1] + " {}. ".format(title),
    if venue:
      print "{{\\em {}}}.".format(" ".join([_.capitalize() for _ in venue.split(' ')])),
      if volume:
        sys.stdout.write(" \\textbf{{{}}}".format(volume))
      if pages:
        sys.stdout.write(", {}".format(pages) if number else " pp. {}".format(pages))
      if year:
        sys.stdout.write(" ({})".format(year))
    if publisher and not venue:
      print "({},{})".format(publisher, year)
    print
    print

sample input

@article{karrer2011stochastic,
  title={Stochastic blockmodels and community structure in networks},
  author={Karrer, Brian and Newman, Mark EJ},
  journal={Physical Review E},
  volume={83},
  number={1},
  pages={016107},
  year={2011},
  publisher={APS}
}

sample output

\bibitem{karrer2011stochastic}
Karrer, B. & Newman, M. Stochastic blockmodels and community structure in networks.  {\em Physical Review E}. \textbf{83}, 016107 (2011)