Try this
%%
K = randi( [1e9,9e9], 1,9 ); % sample data
%%
cac = arrayfun( @(x) num2str(x), K, 'uni',false );
%%
str = string.empty; % or str = cell(1,0);
for ii = 1 : 9
str{end+1} = sprintf( 'l(%d)= %s', ii, cac{ii}(1:3) );
end
str([1,7])
outputs
ans =
1×2 string array
"l(1)= 655" "l(7)= 712"
>>
