Save Data from Table 1 toTable 2

Hi Could Anyone help me regarding on this see image.

I am trying to copy some data in table 1 and table 2 and join them in table 3.

See my response in this post:

https://www.googlecloudcommunity.com/gc/AppSheet-Q-A/Save-Parent-and-Child-in-one-Table/td-p/388652