Try this
filenames = {'11.txt','22.txt','33.txt'};
data = cell(1,numel(filenames));
for i=1:numel(filenames)
data{i} = readmatrix(filenames{i});
end
fig = figure();
ax = axes();
hold(ax);
grid on
view(3);
for i=1:numel(filenames)
plot3(data{i}(:,1), data{i}(:,2), i*ones(size(data{i}(:,1))), 'LineWidth', 1)
end
ax.ZTick = 1:3;
ax.ZTickLabel = filenames;
xlabel('x');
ylabel('y');
zlabel('filenames');
