How we can load embedded Node-red using API?

Http Call -> ${baseUri}/api/ui/;
Display response in iframe but it's not working.

You really haven't given enough information for someone to help you.
Provide a better explaination of what you are trying to do and what you have tried.
Noting the version of Node-RED and node.js (you can find these in the startup log)
The device and OS you are running NR on.
a simple export demonstratitin the issue.

All that would be helpful for someone to helppyou with your issue.