The key to that is in the modem. The modem consumes a lot of power.
You have to check the ublox AT commands manual to send the modem to deep sleep etc. You have to code your own strategy depending on your needs.
The modem is a seperate computer which can only controlled with the AT console and the hardware pins. Libs like ArduinoLowPower.h are only for the Arduino boards.
The modem has to be controlled seperately. All these prebuilt libs from arduino are like guides and examples to start from, especially with the modem and deep down stuff like deep sleep mode etc.
There is also a good ublox guide (search for AT-CommandsExamples_AppNote_(UBX-13001820)