Numbers for OS X Yosemite 10.10.5
Searching Apple Support for iWork for OS X 10.10 turned up a download link for iWork 9.3 however, from what I can tell, it may just be an update installer.  But searching Apple Support is a good place to start.  In order to use the App Store version, one would have to update to OS X 10.12 or higher as noted in the OP's question.