How many calories burnt from 10000 steps?

Did you deliberately walk 5 miles (about 10,000 steps) in addition to your usual daily activity? Then log it as a walk - 20 minutes per mile would be 3 MPH.

If these are your daily steps, then part of these steps have been included in your daily activity level. Here's a chart to figure out what level a 10,000 step day is.
http://www.fitnessforweightloss.com/rate-your-activity-level-based-on-steps-per-day/

It'll vary depending on your height, weight, etc. there's some online calculators you can use to estimate, but are these steps in addition to regular activity or just through a normal day?

https://www.verywell.com/pedometer-steps-to-calories-converter-3882595

I'm 5'1" and 115. Most of my steps are at a brisk pace. My first 10,000 usually get me around 225-250 calories or so.