Please help choosing UPS

I am Ukrainian and I have a lot of problems with electricity right now. I need to select UPS for my requirements. I need to keep online my Wi-Fi router and my cable modem. Also I need to charge my phone and my tablet.

  1. Which kind of UPS I need to buy?
  2. How long will it be online?
  3. How long will it change from minimum value up to maximum value?

Thank you and glory to Ukraine!