Carol can travel insanely fast. The fastest on screen example of this we see is at the end of Captain Marvel when she leaves Earth with the Skrulls and can easily keep up with the ship going at what appears to be lightspeed.
However, we know she can't travel instantaneously so there is some cap to her speed. We know this from the fact that she used the comms system in the meeting with Nat on Earth in Avengers: Endgame whilst she's out helping other planets. If she could just teleport surely she'd be there in person.
Carol Danvers: Listen, fur-face, I’m covering a lot of territory out here. The things that have been happening on Earth have been happening everywhere else. On thousands of planets. You might not see me for a long time.
Of course she can also use the jump points we see dotted around the galaxy as we first see in Guardians of the Galaxy Vol. 2. We also see that there is one on Earth in Captain Marvel. These would cut her travel times down significantly.
Also note that we don't see the full journey of Carol saving Tony/Nebula, for obvious reasons. She appears in front of the Benatar, we get a jump cut and they're landing on Earth. There is no indication for how long it took.
Putting this together we see that she can travel quickly and she has access to travel even faster by using the jump points. However, we don't know how fast she can actually travel, there is no figure to it and no way of really estimating it from what we see on screen.