The Mac App Store requires Sonoma, macOS 14. or later to install the current version of Numbers.
You can get the last compatible version of Pages or Numbers for your OS, provided you have installed Pages or Numbers previously from the Mac App Store and using the same Apple ID. If you haven't, or the Mac had Pages or Numbers preinstalled, then there is no means to get any version of Pages or Numbers now.
Launch the Mac App Store. Sign in with your Apple ID. Press cmd+0 (zero) to open the Purchases panel, and if Pages is there with any indication that it can be installed, then click that. Do not Cancel any subsequent dialogs and this may result in your having the last compatible version of Numbers for your version of macOS.