How do I change steps per mile?

Neither 24 nor 35 steps per mile makes any sense. Steps per mile are typically between 2,000 and 2500 for most people; average about 2200.

But the way to calibrate is to make a 20 minute outdoor walk with a clear view of the sky (so your device can connect to GPS satellites) and it will calculate your pace.

I told you how to do it. Repeating:

But the way to calibrate is to make a 20 minute outdoor walk with a clear view of the sky (so your device can connect to GPS satellites) and it will calculate your pace.