This screen shot is from Keynote for iPad, but Numbers for iPad is pretty much the same:
When you view the file in Preview mode, the title bar of the document should look pretty similar to the above. Over there on the right is the Open in… button.
There might be a button that you have to click first before you see the Open in… button.
Other ways to transfer files to your iPad:
If a field in a CSV file begins with an apostrophe ('
), both Excel and Numbers will treat the field as text, and not render it with any numerical formatting.
Your CSV files appear to try to force text rendering through enclosing number fields in double quotes, but Numbers and Excel don't seem to take the hint that double quote numbers should be treated as strings. The trick seems to be to modify the CSV files so they use the "starts with a single apostrophe" trick rather than the "contained in double quotes" trick for numeric fields, but keep the double quotes for text fields involving punctuation (including commas, quotation marks, line breaks, etc).
To process your CSV files so they do this, you can create an Automator application.
In Automator, create a new Application.
It will have a single action: Run Shell Script (passing input as arguments). Here is the script:
for f in "$@"
do
perl -pi -e "s/\"\"([0-9A-Za-z: \.\-+]+)\"/'\1/g" "$f"
done
Save the resulting application on your Desktop. Drop any CSV files you want to use in Numbers on the application icon, and they will be converted so Numbers should keep the numbers in the fields as literal numbers, and not format them or throw away information.
Back up your data before trying this; it is possible that a particularly oddly constructed string in a record field could throw off the results here.
Best Answer
Select the cell(s) you wish to format and open the Format sidebar > Cell section. Here, choose "Date & Time" and configure the Date entry to an option with full years.
Read more in this Apple Support document: https://support.apple.com/guide/numbers/format-dates-currency-and-more-tan23393f3a/mac