Loading .Mat Files in Nested Sub folders using Dir

I'm working on a project where I need to pull files from this expansive directory with many subfolders nested in folders.

I'm a complete novice when it comes to using matlab and directories, and I was wondering if anyone could help get me started!

I've been using mainFolder = dir(fullfile(uigetfile)) to open the original main directory and then grabbing other folders using more fullfile and wildcards for things they contain. I just don't know how many sub_folders MATLAB will open and let me edit

I've written in english essentially what I need the code to accomplish - I'm not expecting someone to write this for me, just provide me with tips on how to get started!

%function getvariables

%open mainFolder

%open "dates" %name of subfolder in mainFolder

%open "experiment" %name of subfolder in dates

%open "analysis" %name of subfolder in experiment

 if .mat filename includes the string pre
     % pull variables from the .mat file
     % figure out if it contains a certain string of numbers ex. 1234
 if .mat filename includes the string post
     % pull other variables from the .mat file
     % figure out if it contains a certain string of numbers ex. 1234
 else
     % pull other stuff
     % figure out if it contains a certain string of numbers ex. 1234
 end

%load .mat file with the same numbers ex. 1234.mat from ANOTHER folder

%add the variables I grabbed from the pre/post/else .mat files to the loaded 1234.mat file

%save the newly updated 1234.mat file

%run this for a hundred or so different files... Thanks,

ML