Naming your vectors A1,A2,A3 ... then assembling them like this is very inefficient. You want to either load them directly into the matrix (wherever you are getting these variables from) or use a cell array to store them as A{1}, A{2} ... instead. However, I will write down an answer that will work for this case, simply to solve your problem in the short term:
for i=1:n % n is the number of vectors
eval(["Matrix(:,i)=A",num2str(i),";"]; % will evalute the expression - Matrix(:,i)=Ai;
end
