Clear DM's

In dm's there can be a button like this "https://jhpolice.gov.in/sites/default/files/page/sign-language/jhpolice_sl_mrs20.jpg "   when u press it maybe a are u shure? panel and if we continiue we can delete all the mesages. Not the server side the user side. so when I delete them my friend can still have messages. But for me ıt will be like we just started our dm