cant find the search bar on the i tunes store using a mac

The search box is at the top left of the sidebar. Command F will place the cursor there.

Then at the top right of the main window there should be an option to choose where to search (Your Library, Apple Music, or iTunes Store). If that is missing, see the following.

In the Music app menu bar, choose Music > Settings or Preferences > General and insure Show iTunes Store is selected.

Then click in the search box at the top of the left sidebar and then click the iTunes Store option at the top right of the main window as shown in the example in Buy music from the iTunes Store on your iPhone or iPad - Apple Support

If the 3 options don't appear at the top right of the main window after doing the above, 2 things to try:

1) If the View menu in the menu bar contains "Hide Playing Next" or "Hide Lyrics" then click that item so that it changes to "Show Playing Next" or "Show Lyrics."

2) If there is a very small “<” at the top left of the main window (to the right of the sidebar search box), click it one or more times until there is no “<” there.

Closing and reopening the Music app has also been reported to be needed in some cases.

See the first sentence of my previous reply.

See the following from your screenshot below:

After you click in that search box, the three choices (Your Library, Apple Music, or iTunes Store) should appear at the top right of your main window. Click on which of those three you want to search and then enter your search in the same search box at the top of the left sidebar (see red arrow above).

If the 3 choices don't appear when you click in the search box, see my previous post.