A simple way will be to concatenate all the matrixes vertically as all of them have the same number of columns. This can be done by reading the sheets in the excel files and saving it as a cell array and then concatenating the cell array to a matrix.
[~,sheet_name]=xlsfinfo('filename.xlsx');
for k=1:numel(sheet_name)
data{k}=xlsread('filename.xlsx',sheet_name{k});
end;
Iterate over all elements of the cell array and concatenate them using vertcat to form a matrix. Now contourf can be used for plotting.
