There are several problems, such as that you have not converted the row and col character data to numeric (indexing must be numeric or logical), and that you have not accounted for the .jpg file extension in the col string. I suggest that you review the fundamental data types, to avoid confusion between char vectors representing numbers, and actual numeric data.
Here is one solution:
D = 'directory where the files are';
S = dir(fullfile(D,'*-*.jpg'));
N = {S.name};
M = sscanf(sprintf('%s',N{:}),'%d-%d.jpg',[2,Inf]);
C = cell(max(M,[],2));
for k = 1:numel(N)
I = imread(fullfile(D,N{k}));
C{M(1,k),M(2,k)} = I;
...
end
This code assumes that only the jpg files that you need match the
'*-*.jpg'
pattern.
