\documentclass{article}

\usepackage{tikz}
\usepackage{pgfplots}
\begin{document}
\definecolor{mygreen}{HTML}{129d1c}
\pgfplotsset{scaled y ticks=false,scaled x ticks=false}
\begin{tikzpicture}
  \begin{axis}[
      xlabel=$Nombre\ de\ sources$,%0 -> 250 000
      ylabel=$Temps\ moyen\ (en\ ms)$, %0 -> 1 600 000
      ylabel style={xshift=-5pt,yshift=12pt},
      legend cell align=left,
      legend style={draw=none,legend pos=north west,font=\small},
      xticklabel style={/pgf/number format/fixed},
      yticklabel style={/pgf/number format/fixed},
     /pgf/number format/1000 sep={\ }]

    \addplot[color=mygreen,mark=+] plot coordinates {
%      (4,      )
      (20,     16.7)
      (200,    66)
      (1000,   208.6)
      (2000,   359.6)
      (4000,   833.4)
      (6000,   1470)
      (8000,   2409.4)
      (10000,  3610.2)
      (20000,  13436.8)
      (40000,  52300.5)
      (100000, 322164.1)
      (200000, 1250304.9)
    };
    \addlegendentry{Temps moyen phase \#1}

    \addplot[color=blue,mark=+] plot coordinates {
%      (4,      )
      (20,     0.5)
      (200,    6.8)
      (1000,   28.7)
      (2000,   54)
      (4000,   142.7)
      (6000,   223.8)
      (8000,   342.4)
      (10000,  491.4)
      (20000,  1760)
      (40000,  6781.2)
      (100000, 41708.1)
      (200000, 166934.2)
   };
    \addlegendentry{Temps moyen phase \#2}

    \addplot[color=red,mark=+] plot coordinates {
%      (4,      )
      (20,     17.2)
      (200,    72.8)
      (1000,   237.3)
      (2000,   413.6)
      (4000,   976.1)
      (6000,   1693.8)
      (8000,   2751.8)
      (10000,  4101.6)
      (20000,  15196.8)
      (40000,  59081.7)
      (100000, 363872.2)
      (200000, 1417239.1)
  };
    \addlegendentry{Temps moyen total}

    %\legend{$d=2$\\$d=3$\\$d=4$\\$d=5$\\$d=6$\\}
  \end{axis}
\end{tikzpicture}

\end{document}