Your simplest procedure might be this:
Click on the + sign at the top left of the document window to add a Sheet.
Select and delete the Table that is reated with the new sheet.
Open a New document using the same template as you usd for the current document.
Select the (empty) Table(s) on the new document. Copy.
Return to the current document's empty Sheet.
Click on the empty Sheet. Paste.
If necessary, move the pasted Table(s) to match the position of those on the original.
If you think there's a possibility you will need another Sheet, Duplicate the one with the empty table(s) before entering any data onto it.
Notes: "Pages" exist in Numbers only when you print the document, or are preparing to print the document. At all other times, a Numbers document has at least one Sheet—a very large 'canvas' on which may be placed one or more Tables, Images, Charts, Text boxes or other objects.
Each Sheet starts with a minimum of one Table. More Tables may be added to the Sheet.
Each Table consists of at least one Cell. A Numbers table may consist of up to 255 columns or about 16,300 rows, but the practical limit for a table containing formulas is less than that, as the document tends to slow down as rows are added.
Each cell may contain an entered value, or a formula which creates a value, but cannot contain both.