The growth section of ProfitWell will give you the tools to break down your growth by plan and by "new vs. existing" users. 

Total Growth:

Total growth is the net amount of subscription revenue added in a given month.

This is the sum of the revenue added from new customers and existing customers. It's positive when revenue added via new customers and upgraded subscriptions is greater than revenue lost due to downgrades and cancelled customers

Growth from New Users:

Growth from new users measures the total amount of subscription revenue that you’ve added from new customer signups for your product.

Growth from Existing Users:

Growth from your existing users is calculated by subtracting the value of all subscription downgrades and churn from the value of all subscription upgrades. In other words, this is how much your business would grow or shrink if you didn’t add any additional customers.