Searching iTunes store

I'm having problems searching for music in the iTunes store. I have the store in the side bar on the left of the screen but when I click in the search box there is no option to select the store as a search location - it just says 'searching your library'.

I read an earlier post saying that when you click in the search box 3 dots appear on the right. I do have three dots but they only open 'playing next' and 'history' options.

I would love to buy and download some more music!