Transferring cell values from one Numbers sheet to another

If the ending balance is in a footer row it is pretty simple. If the ending balance is in June 2024::Table 1::D20 (where row 20 is a footer row) then the formula is

=June 2024::Table 1::D20

The formula might have started out pointing at cell D3, not D20, but as the table grew, the footer row kept moving down and the formula kept pointing to it.

If the balance is in whatever the bottom row happens to be of the last month's table, it is a more complicated formula that has to determine what that last data row is.

If in the last row but it is not a footer row:

=INDEX(June 2024::Table 1::D,ROWS(June 2024::Table 1::D))

If not in the last row (i.e., there might be blank rows below it), a lookup doing a bottom-to-top search might be the best solution

=XLOOKUP(REGEX(".+"),June 2024::Table 1::D,June 2024::Table 1::D,"No data available",2,−1)