How to combine two windows as one in Terminal?

In Terminal I can use Command + T to create Tabs in one Window, check below:

but now, I opened two windows like this, how to merge them as one liker upper:

I have tried drag one into another, but not work.

my macos Version is: Catalina 10.15.7 (19H524)

If you want to be able to drag one into another, you have to turn the Tab Bar on from the View menu, or use ⇧⌘T, and then drag the tabs. Both the source and the destination need to have the Tab Bar turned on.

Or, from the Window menu... Merge All Windows.

You can use this way in Terminal Menu bar:

Window -> Merge Window -> Merge All Windows