So while setting up the goals in Google Analytics, if you Chargebee's Thank You Page is already configured, then under the 'Destination' section, the following text needs to be entered - '/thank_you'.
This would help the goal to get triggered when the destination reaches the configured URL.
Also, incase of a custom based Redirect URL configuration {own 'Thank You' page}, its appropriate path as a part of the Goal URL should be entered.
Here's a document which gives an overview on how to set up these goals.
Google Universal Analytics is getting deprecated and will stop processing data on July 1, 2023. Google has introduced a new analytics engine Google Analytics 4 (GA4) that offers new and advanced features that can help you gain a deeper understanding of your website visitors' behavior, such as event tracking, machine learning, and cross-device tracking. With the new setup of GA4 and Chargebee-hosted pages it leverage the capabilities to analyze and optimize your website's performance, providing you with a competitive edge in the subscription business. If your site is configured with Google Universal Analytics version, then you can refer to this link to migrate to Google Analytics 4.
If you're using Google Tag Manager to connect to your Google Analytics 4, we recommend that you use this separate integration, and never both.