Cost of iCloud plan and what plan do I have

See the following for prices: iCloud storage plans and pricing - Apple Support

To see your current plan from an iMac:

1. Choose Apple menu  > System Preferences, then click Apple ID. If you’re using macOS Mojave or earlier, you don’t need to click Apple ID.  
2. Click iCloud.
3. Click Manage. (at bottom right of the window)
4. See the plan at top left of the window.

nancykay wrote:

How do I find out my payment plan and how much I am paying for ICloud

iCloud storage plans and pricing - Apple Support