Read this support article for instructions on how to upgrade to iCloud+ --> Buy iCloud+ or upgrade your current storage plan - Apple Support
- The article includes instructions for various hardware and managing your plan. Select the hardware you own.
You should upgrade right now. Since the subscription has ended you are automatically downgraded to the free 5GB plan. Because you have effectively downgraded, make sure you read the section "What happens when you downgrade or cancel iCloud+" in this support article Downgrade or cancel your iCloud+ plan - Apple Support
What happens when you decrease your storage plan
● If your iCloud storage exceeds your new storage plan capacity, iCloud won't sync or update your information, and iCloud backups won't complete. iCloud starts syncing again and iCloud backups resume when you increase your storage capacity or delete information to make more space.
Apple will leave the excess current content in place but might eventually remove it so upgrade while it is still there or at least put it on alternative archival storage.
Oh, and speaking of archival storage. iCloud is should not be considered as archival storage or long-term backup. It is really designed as syncing storage for items used frequently from multiple devices and short-term backup so if, say, you take a photo with your iPhone and then an hour later you break the iPhone, the photo may have been backed up already.
