VS Tool Find and Replace

Hi guys, 

I'm using VS code to develop the html page, my page with some class like .Box, .Box-child1, Box-child2, jsut a sample, really more than these.   

I suppose to use VS regex function to find Box, Only just need found Box instead of includ .Box-child1, Box-child2, could you provide a sample or code to achieve it? 

Note: If I post the wrong place, please note me! 

Queen