By default, the Search option isn't available on the Desktop Toolbar in Windows 10.  But enabling the option is very simple.

Right-click the Desktop Toolbar on any open area of the bar.  

Click the icon on the drop open menu that says Cortana.

Click the option to show search box.

Now you have a search box on the Desktop Toolbar.  Type whatever you are looking for in the search box and Windows will do it's best to display it.  Examples;  as you type the word calculator in the search box the results will display Calculator.  As you type the word Excel inthe search box the results will display Excel.  Click the icon displayed to open the item you need.

If you know the name of a file or folder Windows can find that too.