Hello,
The $99 is upgrade license only. Meaning, you must have an already activated Home edition to use it.
The other one is full license, meaning, you can install it directly, it doens't require an already activated Home edition to use it.
If you are already on Home edition and it is already activated, this is what you can do after purchase:
You can go to Settings > System > Activation > Change product key
Disconnect internet, and disable any third party antivirus, key in the generic key instead: VK7JG-NPHTM-C97JM-9MPGT-3V66T
That should get you to Pro. Once restarted, you can connect back to the internet, sign into your Microsoft account. See if it is activated.