Adapting posts to columns using Flexbox

All good, people? Next I have a site that I need to call the latest posts from a category of id = 3 within 2 rows with 3 columns in home, something that would be very easy using bootstrap repeating 6 div with class ".col-sm-4" for example . But in my case I have a div with 3 columns and each column has 2 images one below the other and in the middle is bigger the height and width, only the html and css I have already done, the call is also done but I wanted to call 2 by time in each column and middle column would call the class that would make it increase. Currently it is as in the appendix named test.jpg and wanted it to look the same in index.png!