If you have tortoiseSVN installed, you could check it by clicking “Repo-browser”:
The team server URL can be found in sprintr, under Develop/Team Server in the side bar,
The team server will contain all branches.
Hope this helps
If you are looking for the API for how to get a specific package from a specific branch, check out this documentation here:
https://docs.mendix.com/apidocs-mxsdk/apidocs/team-server-api#retrieve-branches
Note that the URL references an AppID parameter, which is the subdomain name of the node and is a string instead of the numerical ID.