Start10 turns the start button into Win 7 start behavior down to just about every nuance, including the search box. However, Win10 Start Menu still has that search feature it just does not show as a box, simply click on the Start button, the start menu will pop up, then simply start typing what you want to search for...
Like this.
1. Click start button
2. Type "Internet Explorer"
I highly recommend start10 though, well worth the money, in fact, I would recommend Object Desktop (a full suite of customizing apps). Stardock has done a superb job of 'fixing' the utterly horrid Win 10 interface issues. Sometimes I think Win10 icons, colors, buttons, and such were designed by a retarded 2 year old orangutan.