How to move submissions from a spreadsheet to another ?

I have a new question... when I make adjustments to the spreadsheet, such
as moving old submissions to a new tab, and then the new submissions won't
show up. How do I sync new submissions to the current spreadsheet?
here are the two screenshots - main spreadsheet is the sheet my company
uses and we tend to have complete orders move to new tab under "orders
completed"... new submissions created since last night won't show up on the
main spreadsheet.
I unlinked and then when I integrated it, it created a new spreadsheet
instead. how do I sync new submissions to the main spreadsheet?
Thanks!

You can not edit the spreadsheet where you are receiving your submissions, it will brake the integration and I think that is the reason why you are not receiving your submissions.

Now, if I can understand your request correctly, you are trying to sync your new submissions with an old spreadsheet ? 

Unfortunately, that is not possible, the process should be manually and you would have to copy and then paste the submissions in the old/new spreadsheet.

However, when you remove the integration and re-integrate your form again with Google Spreadsheet you will keep the same spreadsheet if you have not changed anything, I tried sometimes and I can see it uses the same spreadsheet if you do not change anything.

Hope this will help you.

Do let us know if you have more questions or need more help, we will be glad to assist you.

Regards.