documentclass{article}
usepackage{pgfplots}

begin{document}
begin{figure}[h]
%caption{Graph showing the proportion of children born into each partnership
%scenario by ethnic group (Table 5, Kiernan and Smith, 2003)}
centering
begin{tikzpicture}
begin{axis}[
ybar stacked,
legend style={at={(0.47,1.05)},
  anchor=south west,legend columns=-1},
  %x axis line style = { opacity = 0 },
  %y axis line style = { opacity = 0 },
  tickwidth = 2pt,
bar width=5pt,
 ylabel={Number of Rounds},
symbolic x coords={LEACH 50 Nodes, LEACH-MAC 50 Nodes,
Proposed 50 Nodes,LEACH 100 Nodes,LEACH-MAC 100 Nodes,Proposed 100 Nodes,LEACH 200 Nodes,LEACH-MAC 200 Nodes,Proposed 200 Nodes,LEACH 250 Nodes,LEACH-MAC 250 Nodes,Proposed 250 Nodes},
xtick=data,
x tick label style={rotate=90,anchor=east},
]
addplot  coordinates {(LEACH 50 Nodes,146) (LEACH-MAC 50 Nodes,211)
(Proposed 50 Nodes,870)  (LEACH 100 Nodes,172) (LEACH-MAC 100 Nodes,219)
(Proposed 100 Nodes,980) (LEACH 200 Nodes,249) (LEACH-MAC 200 Nodes,322)
(Proposed 200 Nodes,660) (LEACH 250 Nodes,318) (LEACH-MAC 250 Nodes,465)
(Proposed 250 Nodes,1025) } ;
addplot   coordinates {(LEACH 50 Nodes,115) (LEACH-MAC 50 Nodes,109)
(Proposed 50 Nodes,22)  (LEACH 100 Nodes,67) (LEACH-MAC 100 Nodes,102)
(Proposed 100 Nodes,26) (LEACH 200 Nodes,50) (LEACH-MAC 200 Nodes,113)
(Proposed 200 Nodes,675) (LEACH 250 Nodes,65) (LEACH-MAC 250 Nodes,34)
(Proposed 250 Nodes,263) };
addplot  coordinates {(LEACH 50 Nodes,799) (LEACH-MAC 50 Nodes,714)
(Proposed 50 Nodes,530)  (LEACH 100 Nodes,941) (LEACH-MAC 100 Nodes,908)
(Proposed 100 Nodes,362) (LEACH 200 Nodes,945) (LEACH-MAC 200 Nodes,830)
(Proposed 200 Nodes,33) (LEACH 250 Nodes,859) (LEACH-MAC 250 Nodes,781)
(Proposed 250 Nodes,56) };
legend{FND, TND, LND}
end{axis}
end{tikzpicture}
end{figure}
end{document}

documentclass{article}
usepackage{pgfplots}
pgfplotsset{compat=1.16}
begin{document}
begin{figure}[h] %
caption{Graph showing the proportion of children born into each partnership %
scenario by ethnic group (Table 5, Kiernan and Smith, 2003)}
centering
begin{tikzpicture}
begin{axis}[ybar stacked, legend style={at={(0.47,1.05)}, anchor=south west,legend columns=-1}, %
x axis line style = { opacity = 0 }, %
y axis line style = { opacity = 0 }, tickwidth = 2pt, bar width=5pt, ylabel={Number of Rounds},
symbolic x coords={LEACH 50 Nodes, LEACH-MAC 50 Nodes, Proposed 50 Nodes,
dummy,
LEACH 100 Nodes,LEACH-MAC 100 Nodes,Proposed 100 Nodes,
dummy,
LEACH 200 Nodes,LEACH-MAC 200 Nodes,Proposed 200 Nodes,
dummy,
LEACH 250 Nodes,LEACH-MAC 250 Nodes,Proposed 250 Nodes}, xtick=data, x tick label style={rotate=90,anchor=east}, ]
addplot coordinates {(LEACH 50 Nodes,146) (LEACH-MAC 50 Nodes,211)
(Proposed 50 Nodes,870) (LEACH 100 Nodes,172) (LEACH-MAC 100 Nodes,219)
(Proposed 100 Nodes,980) (LEACH 200 Nodes,249) (LEACH-MAC 200 Nodes,322)
(Proposed 200 Nodes,660) (LEACH 250 Nodes,318) (LEACH-MAC 250 Nodes,465)
(Proposed 250 Nodes,1025) } ;
addplot coordinates {(LEACH 50 Nodes,115) (LEACH-MAC 50 Nodes,109)
(Proposed 50 Nodes,22) (LEACH 100 Nodes,67) (LEACH-MAC 100 Nodes,102)
(Proposed 100 Nodes,26) (LEACH 200 Nodes,50) (LEACH-MAC 200 Nodes,113)
(Proposed 200 Nodes,675) (LEACH 250 Nodes,65) (LEACH-MAC 250 Nodes,34)
(Proposed 250 Nodes,263) };
addplot coordinates {(LEACH 50 Nodes,799) (LEACH-MAC 50 Nodes,714)
(Proposed 50 Nodes,530) (LEACH 100 Nodes,941) (LEACH-MAC 100 Nodes,908)
(Proposed 100 Nodes,362) (LEACH 200 Nodes,945) (LEACH-MAC 200 Nodes,830)
(Proposed 200 Nodes,33) (LEACH 250 Nodes,859) (LEACH-MAC 250 Nodes,781)
(Proposed 250 Nodes,56) };
legend{FND, TND, LND}
end{axis}
end{tikzpicture}
end{figure}
end{document}