Welcome to the Atlassian Developer Community, @TimothyGodfrey.
Backreading the thread, @sunnyape’s answers are accurate (as always, thanks @sunnyape for the active participation in the community).
I’ll try to unpack some of the items you mentioned here.
If you are looking for Get content REST API, then it should be
https://{my-instance}.atlassian.net/wiki/rest/api/content
This documentation link is for the Confluence server; the Confluence Cloud REST API counterpart can be found here.
This is an error and not a notice. This is also returned if the API token you used is incorrect. You can try creating a new API token and running the script.
I tried the following script on my terminal and it works as expected,
curl -X GET https://my-instance.atlassian.net/wiki/rest/api/content -H 'Content-Type: application/json' --user 'ian_email@atlassian.com:API_TOKEN'
In order to have a better understanding of where you are currently, can you share the script you are using (with the credentials redacted)?
Hope this helps,
Ian