Hi Max Muhammad,
Thank you for posting query in Microsoft Q&A Platform.
Inside dataset you cannot access activity outputs. It's out of scope of dataset. Hence you are seeing that error.
You can consider having a parameter created inside dataset and then wherever you are using that dataset (In copy activity may be), that time you can pass value to it from other activities if they are connected.
Please check below screenshots, here web activity (submit job) gets queryId
and then in copy activity, I used parameterized dataset and finally passing queryId
from first web activity to copy activity.
Hope this helps. Please let me know how it goes and if any further queries.
Please consider hitting Accept Answer
button. Accepted answers help community as well.