I need an older pages for my iMac High Sierra V10.13.6

Open the Mac App Store & hold down the option key while clicking the Purchases tab on your High Sierra Mac. If you see Pages, Numbers, and Keynote with Update/Install buttons, it may offer to download a previous version of these applications compatible with High Sierra.

See VikingSOX's reply in this discussion in the Pages for Mac forum.

Unless you had it before & can find it in the AppStore>Purchases, then you're out of luck, unless this helps...

Look into the Free LibreOffice, it handles MS Office files like Word & Excel, & Page Layout…

https://www.libreoffice.org/