If all the files have the same structure/data format, you can use datastore to merge them:
fileNames = {'t1.txt', 't2.txt', 't3.txt'}
ds = readall(datastore(fileNames)); % change other properties if needed
otherwise, you can use readtable within a loop
fileContents = {};
fileNames = {'t1.txt', 't2.txt'};
for i = 1:numel(fileNames)
fileContents{i, 1} = readtable(fileNames{i});
end