If I streamed at 1000kbps for 2-3 days, how many gigabytes would it take up on my internet bill?

Let's do the math.

1000kbps is about 100kBytes/sec, considering overhead. That is about 6 MBytes/minute. 1440 minutes in a day makes it about 8,640MBytes/day or 8.6GBytes/day

say 3 days, that would be almost 26GBytes of data, assuming steady speed.

This all assumes your original units are correct, 1000kbps is 1 megabit/sec download speed, not 1000kBps, which would be 1000kBytes/sec = 1 MegaBytes/sec.

If your original units are wrong, and you meant "bytes/sec", not "bits/sec", then multiply the 8.6GBytes total by 10 (approx. 86 GBytes)

that's only one megabit  per second  so around 7.5 megabytes a minute , not much at all

Simple math - kbps times seconds you plan to stream

I do that all the time and my price doesn’t change 

172.8 to 259.2 gigabytes.