why can't i download itunes

iTunes was replaced by Music.App & Finder functions.

In recent versions of macOS, iTunes functions have been replaced by other softwares. For the purpose of restoring your iPad, see Restore your iPhone, iPad, or iPod to factory settings for how to do this via Finder:

"Restore your device to factory settings

1. On a Mac with macOS Catalina or later, open the Finder. On a Mac with macOS Mojave or earlier, or on a PC, open iTunes. Find out which macOS your Mac is using.
2. Connect your device to your computer.
3. If a message asks for your device passcode or to Trust This Computer, follow the onscreen steps. Get help if you forgot your passcode. 
4. Select your device when it appears on your computer. Learn what to do if your iPhone, iPad, or iPod touch is unresponsive or won't turn on. Or get help if your device doesn't appear on your computer.
5. Click Restore [device]. If you're signed into Find My, you need to sign out before you can click Restore.
6. Click Restore again to confirm. Your computer erases your device and installs the latest iOS, iPadOS, or iPod software.
7. After your device restores to factory settings, it restarts. Now you can set it up as new."

To learn about other functions that used to be completed in iTunes, visit What happened to iTunes?

iTunes is not available as a separate download. Plus it was replaced by Music starting with Catalina 10.15.

What OS is the MacBook running?