Whether it’s possible via the Republic app depends upon which phone you have. If you have a new 3.0 phone, it’s no longer possible to use the Republic app for this purpose. Similar information is available in the Android settings app. You might also check your monthly emailed invoices. Mine show cell data use for the month covered.
Please note what I’ve written above presumes you are interested in historical cell data use going back more than a month. While still possible with the Republic app on legacy phones (Moto E1, E2, G1, G3, X1 and X2) only the current month is available via the Republic app on a 3.0 phone.