Insert rows from one numbers file into another numbers files WITHOUT overwriting existing data

OS 13.5.2. 2019 macbook pro:

I have looked at some other threads and see some snarky responses about questions being asked and answered, but I have not found that the suggestions are working, so I'm starting a new thread and do not need snarky answers about the question being asked and answered. None of what has been suggested seems to be working. I'll update if I find something.

Here's the situation. I have 58 rows with 6 columns in file A. I have the same column titles in file B along with 200 rows of credit card data (date, merchant, amount, etc...same as file A). I just need to insert the 58 rows from file A into the top of file B WITHOUT overwriting existing data in File B.

I have done it before by just copy/pasting or highlighting and dragging from A to B, but it is sporatic and I have no idea what I do differently when it does work.

In older PC excel sheets, you could set things to Insert vs Overwrite, but I cannot find a similar setting. I know this is possible as I have done it before.

Could somebody please give me a specific setting or sequence of steps to insert the rows/columns? I know I need to insert a row under the header row (the gray row with column titles) where I want to insert the data. Manually creating 58 columns seems unnecessary, and when I try to create 4 or 5, then copy/paste them results in the same overwriting of rows under them.

Thanks!

Jon