How can I track my MacBook laptop's internet data usage

View network activity in the Activity Monitor window

• In the Activity Monitor app  on your Mac, click Network (or use the Touch Bar) to see the following at the bottom of the window:
  • Packets in, Packets out: The total number of packets received and sent.
  • Packets in/sec, Packets out/sec: The speed of information being transferred (in packets per second). This number can be displayed in the graph.
  • Data received, Data sent: The total amount of information moved (in megabytes).
  • Data received/sec, Data sent/sec: The amount of information moved over time (in bytes per second), also called throughput. This number can be displayed in the graph.
• To display more columns, choose View > Columns, then choose the columns you want to show

See this Link for further reference

View network activity in Activity Monitor on Mac – Apple Support (UK)

Directly measuring your Internet data usage is impracticable since a Mac only connects directly to the router connected to the Internet. Therefore it is the only device that can accurately record the amount of Internet data you're using. I don't know of any routers with such reporting capability, but they might exist.

The total amount of network traffic to and from your MacBook over a period of time can be recorded, which might be useful to you. ‎Bandwidth+ on the Mac App Store can do that.