How to read two files simultaneously?

I have a pair of files such as Arenosillo.2007.047.12.07.G18.txt and Arenosillo.2007.047.12.07.ion.txt. I have such 500 pairs. I have to read data from both the files and plot them. The code I wrote is not working because of two for loops. Can anyone please help? I am working with MATLAB R2015a.

list1=dir('Arenosillo*ion*');
list2=dir('Arenosillo*G*');
for n=1:length(list1) 
    for i=1:length(list2)
    filename1=list1(n).name;
    filename2=list2(n).name;
    filename_edit=strrep(filename2,'.',';');%make textscan easier
    part=textscan(filename_edit,'Arenosillo;%d;%d;%d;%d;%s');
    delimiterIn = ' ';
    B = importdata(filename2,delimiterIn);
    A = importdata(filename1);
    Altitude1 = A.data(:,1);
    Altitude2 = B(:,1);
    Digisonde = B(:,2);
    COSMIC = A.data(:,7);
    OcculationAz = A.data(:,5);

    figure 
 
   [hAx,hLine1,hLine2] = plotyy(Altitude1,OcculationAz,[Altitude1',Altitude2'],[COSMIC',Digisonde']);

   hLine1.Marker = 'o';
   hLine2.Marker = '*';

    title('Variation of Electron Density and Occultation Azimuth with Altitude')
    xlabel('Altitude (Km)')
    ylabel(hAx(1),'Occultation Azimuth (deg)') % left y-axis 
    ylabel(hAx(2),'Electron Density (/m3)') % right y-axis 
   
    legend('Occultation Azimuth','COSMIC','Location','NorthEastOutside')
    
    saveas(gcf,sprintf('Arenosillo.%04d.%03d.%02d.%02d.jpg',part{1},part{2},part{3},part{4}))
    end  
end

Answer 1

[KSSV]

files = dir('*.txt') ;
N = length(files) ;
for i = 1:N
    thisfile = files(i).name ;
    % do what you want, load and plot
end

[SGMukherjee]

This worked. Thank you so much.