Insert row in iPad numbers spreadsheet

To insert a row at the bottom of the page, tap the little “=“ icon at bottom left of the sheet. To insert a row anywhere else, tap an entry in any row; this will reveal a column of row numbers on the left of the sheet. Now tap the row number; a menu will appear including a “row actions” option.

You might find the Numbers User Guide useful:

https://support.apple.com/en-gb/guide/numbers-ipad/welcome/ipados

You’ll also find a downloadable version of the Guide in the Apple Books App.