I am unable to sync my iPad whilst there is enough memory space

Perhaps the error that you see refers to your available iCloud storage - and not your iPad's internal storage.

Unless you subscribe to a higher iCloud+ storage tier, you will only have 5GB of iCloud storage for all of your synchronised photos, documents and iCloud backups of your iPad.

Manage your iCloud storage - Apple Support

Upgrade to iCloud+ - Apple Support

iCloud+ plans and pricing - Apple Support

If you are not using iCloud, with what are you attempting to synchronise your iPad?

If synchronising data and settings between Apple devices (such as a Mac computer, iPhone or iPad) - you need to use iCloud. From iPad settings:

Settings > [Your Name / AppleID] > iCloud - enable Apps and Apple services that you wish to synchronise as required

More information about iCloud - and how it can be used - can be found here:

iCloud User Guide - Apple Support